Licensing

[privefl]

Beware that if you're linking to the code from {Rcpp}, which you do, you have to use a GPL license. Right, @eddelbuettel?

[eddelbuettel]

No, not a stated requirement from our end. Rcpp is GPL (>= 2) as is R, so the aggregate will be GPL'ed but the actual software you write and combine with it can be whatever is compatible.

To look at numbers, you can start with db <- tools::CRAN_package_db(), feed that into tools::package_dependencies(...) to find reverse dependencies of Rcpp, index the db accordingly and then tabulate the License: field.

The result is not all that pretty or clean (in the 'too many "spelling variants" of the same license) but you will see plenty of GPL'ed packages, and a fair number of MIT licenses and alike. Including some Apache 2 as for this package.

[privefl]

But MIT and Apache are compatible with GPL only one-way, right? E.g. I read

Apache 2 software can therefore be included in GPLv3 projects, because the GPLv3 license accepts our software into GPLv3 works. However, GPLv3 software cannot be included in Apache projects. (https://www.apache.org/licenses/GPL-compatibility.html)

[hyacz]

As @eddelbuettel said, I listed the license information for packages that depend directly on Rcpp

> db <- tools::CRAN_package_db()
> p <- sapply(db$Package, FUN=function(x){ "Rcpp" %in% tools::package_dependencies(x, db)})
> db1 <- db[p,]
> table(db1$License)

        AGPL | file LICENSE              Apache License
                          1                           1
    Apache License (>= 2.0)       Apache License (>= 2)
                          1                           1
         Apache License 2.0 BSD_2_clause + file LICENCE
                          4                           1
BSD_2_clause + file LICENSE BSD_3_clause + file LICENSE
                          5                           5
                    BSL-1.0                EPL (>= 1.0)
                          2                           1
                    FreeBSD                         GPL
                          1                           5
               GPL (>= 2.0)                  GPL (>= 2)
                          1                          72
  GPL (>= 2) | file LICENSE                  GPL (>= 3)
                          2                          10
                      GPL-2        GPL-2 | file LICENSE
                         12                           1
                      GPL-3        GPL-3 | file LICENSE
                         22                           1
                     LGPL-3          MIT + file LICENCE
                          3                           1
         MIT + file LICENSE                     MPL-2.0
                         44                           1
     MPL-2.0 | file LICENSE
                          1
>

since Rcpp is GPL, this aggregate will be GPL, but part of it (this package) can be any GPL compatible protocol. It is ok for a GPL aggregate to include an Apache or MIT part.

https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html ... In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License. ...

To avoid causing more confusion, we will change the license to GPL-3 for better compatibility with dependencies such as Rcpp. Thank you for the discussion.

[eddelbuettel]

Your count is (way) too small up there. We are at almost 2500 packages.

> library(data.table)
> db <- data.table(as.data.frame(tools::CRAN_package_db()), key="Package")
> rcpp <- data.table(Package=tools::package_dependencies("Rcpp", db=db, reverse=TRUE)[[1]], key="Package")
> rcppdb <- db[rcpp]
> dim(rcppdb)
[1] 2499   66
> tt <- table(rcppdb$License)
> tt[order(tt, decreasing=TRUE)]

                            GPL (>= 2)                                  GPL-3 
                                   737                                    601 
                    MIT + file LICENSE                                  GPL-2 
                                   349                                    220 
                            GPL (>= 3)                                    GPL 
                                   216                                     39 
           BSD_3_clause + file LICENSE                   GPL-3 | file LICENSE 
                                    29                                     27 
                         GPL-2 | GPL-3                     Apache License 2.0 
                                    24                                     20 
                                LGPL-3              GPL (>= 2) | file LICENSE 
                                    18                                     17 
                                AGPL-3            BSD_2_clause + file LICENSE 
                                    15                                     14 
                          GPL (>= 2.0)                                    CC0 
                                    14                                     13 
             GPL (>= 3) | file LICENSE                           GPL (>= 3.0) 
                                    10                                      9 
               Apache License (== 2.0)                   GPL-2 | file LICENSE 
                                     7                                      7 
                           LGPL (>= 3)                                MPL-2.0 
                                     6                                      6 
                                  LGPL                  AGPL-3 | file LICENSE 
                                     5                                      4 
               Apache License (>= 2.0)                  Apache License (>= 2) 
                                     4                                      4 
                              CeCILL-2             GNU General Public License 
                                     4                                      4 
           LGPL-3 | Apache License 2.0                         Apache License 
                                     4                                      3 
     Apache License 2.0 | file LICENSE                   Artistic License 2.0 
                                     3                                      3 
                       CC BY-NC-SA 4.0                                 CeCILL 
                                     3                                      3 
                          file LICENSE                            LGPL (>= 2) 
                                     3                                      3 
                 LGPL-3 | file LICENSE                     MIT + file LICENCE 
                                     3                                      3 
                           AGPL (>= 3) Apache License (== 2.0) | file LICENSE 
                                     2                                      2 
           BSD_3_clause + file LICENCE                                BSL-1.0 
                                     2                                      2 
     GNU General Public License (>= 3)                          LGPL (>= 2.1) 
                                     2                                      2 
                              LGPL-2.1                                    ACM 
                                     2                                      1 
                   AGPL | file LICENSE                           Artistic-2.0 
                                     1                                      1 
   BSD 3-clause License + file LICENSE            BSD_2_clause + file LICENCE 
                                     1                                      1 
                             CC BY 4.0                           CC BY-SA 4.0 
                                     1                                      1 
                          EPL (>= 1.0)                                   EUPL 
                                     1                                      1 
                         EUPL (>= 1.2)                                FreeBSD 
                                     1                                      1 
                          GPL (>= 2.1)     GPL-2 | GPL-3 | MIT + file LICENSE 
                                     1                                      1 
            GPL-2 | LGPL-2.1 | MPL-1.1             GPL-2 | MIT + file LICENSE 
                                     1                                      1 
   GPL-3 | BSD_2_clause + file LICENSE                       GPL-3 | LGPL-2.1 
                                     1                                      1 
                    LGPL (>= 2.0, < 3)      LGPL (>= 2.0, < 3) | file LICENSE 
                                     1                                      1 
            LGPL (>= 2) | file LICENSE                          LGPL (>= 3.0) 
                                     1                                      1 
                                LGPL-2            LGPL-2 | Apache License 2.0 
                                     1                                      1 
    Mozilla Public License Version 2.0                           MPL (== 2.0) 
                                     1                                      1 
                          MPL (>= 2.0)                             MPL (>= 2) 
                                     1                                      1 
             MPL (>= 2) | file LICENSE MPL (>= 2) | GPL (>= 2) | file LICENSE 
                                     1                                      1 
                MPL-2.0 | file LICENSE                              Unlimited 
                                     1                                      1 
> 

That shows that GPL (in my forms) dominates, that MIT/BSD are clearly present, and that there are over 40 Apache licensed packages --- just among those using Rcpp!

So to repeat, you are not required to change your license. CRAN won't care.

That said, I personally like and prefer GPL (>= 2) for work I do as an open source contributor -- I like other people to enjoy it and I like them to reciprocate under the same terms. I do not think I want work I do in my spare time to end up in a closed source project from which no code improvements may flow back so to me BSD, MIT, ... never had any appeal. (That said I do have a day job where I write MIT-licensed open source software as well as some parts that remain closed. It all depends on cicumstances.)

So to make a long story short, at best @privefl and I could appeal to you to change your license to be closer to the model R itself uses. That was always a strong enough reason for me, but it is not anything enforced by license terms as initially claimed here.

[hyacz]

@eddelbuettel Thank you for the detailed code example and clear explanation! We are new to the open-source license and the main reason for choosing Apache is its first option for GitHub LICENSE file templates. Open source is a great thing, we learn from and give back to the community, and we have learned a lot from the discussion.

[eddelbuettel]

Ahhh, thanks for the context! Yes, there are a few other (decent) sites out there to make an informed license choice, sadly all this gets a little overloaded with "politics" (i.e. python/julia has much more use of MIT/BSD and sometimes refuses to include GPL code; over here in R land (as in my personal view) GPL is often seen as much more foundational). After all it is a little personal: I care about my rights as author and user.

Maybe have a look here: https://choosealicense.com/

[hyacz]

@eddelbuettel Thank you for your suggestion, this site is exactly what we needed. 😄 I've read your book and a lot of example code, but I didn't expect to be able to chat with you in such a simple way.

[eddelbuettel]

All good. Forgot to add a point to my preceding post: It's best to not be judgemental; most people who contribute to open source on their own time and motivating and all we should care about is that the license choice keep things can inter-operate and use each other (i.e. are license-compatible too).

After that, it's personal preferences. Just how some crazy people may use an OS I would not use or an editor I would not deploy :grinning: