Please clarify licenses of source code and documentation

DISCLAIMER: Despite having contributed a lot to POV-Ray in the past, I am NOT in any position to make any authoritative statements about legal matters of the POV-Ray project whatsoever. Also, I AM NOT A LAWYER.

That said, my personal interpretation of the situation is as follows:

POV-Ray is licensed to the end user under the AGPL 3, period. No alternatives, unless explicitly and individually agreed upon between Persistence of Vision Raytracer Pty. Ltd. and the end user. For example, you can't use the Windows binaries in any way that conflicts with the provisions of the AGPL 3, even if some later AGPL would include provisions to allows such use. (*)
POV-Ray is licensed to authors of derivative works under the AGPL 3 or any later version. Most notably, you could modify POV-Ray in a manner that conflicted with the AGPL 3, provided you would do so in full compliance with any particular later AGPL.

My personal understanding is that this was a deliberate choice, serving the following purposes:

It restricts the current choice of end-user license for POV-Ray proper to a well-defined version of the AGPL.
It retains the option to license future versions of POV-Ray proper under a different version of the AGPL, without having to go through the hassle of re-licensing all the source code from the respective contributors.

(* Note that this presumably applies not only to official Windows binaries, but also any binaries built by the end user (e.g. on Linux or macOS) or a 3rd party from official unmodified source code: To use it under a later AGPL, you would technically have to create a derived work first, which you could choose to put under a later AGPL, and then use that derived work. But you would have to give such a derived work a different name, as the term "POV-Ray" is a trademark.)

Again, this is my personal interpretation of the situation.

POV-Ray / povray

Please clarify licenses of source code and documentation #391