The Solaris Porting Layer, SPL, is a Linux kernel module which provides a compatibility layer used by the ZFS on Linux project.
The latest version of the SPL is maintained as part of the ZFS on Linux Github repository:
Cloning this repository is only needed when building version 0.7.x or earlier.
The SPL is released under a GPLv2 license. For more details see the NOTICE
and LICENSE files; UCRL-CODE-235197