CC BY-SA 4.0 now one-way compatible with GPLv3
The Creative Commons has announced that a
"detailed
analysis" has determined that materials licensed under BY-SA 4.0
license may be distributed under the terms of GPLv3. "But if your
use case calls for or requires (in the case of remixing CC BY-SA 4.0 and
GPLv3 material to make a single adaptation) releasing a CC BY-SA 4.0
adaptation under GPLv3, now you can: copyright in the guise of incompatible
copyleft licenses is no longer a barrier to growing the part of the commons
you’re working in. We hope that this new compatibility not only removes a
barrier, but helps inspire new and creative combinations of software and
culture, design, education, and science, and the adoption of software best
practices such as source control (e.g., through “git”) in these
fields."