VVVVVV - packaging with a license exception

[computermouth <computermouth@proton.me>]

Howdy Debian Mentors,

My name is Ben Young, I maintain a little Debian image that has a few users (called CrunchBangplusplus), and I build some simple packages for it.

I also do a bit of gamedev in my spare time. I'd like to start packaging some games for Debian, and I started looking with a game called VVVVVV.

https://store.steampowered.com/app/70300/VVVVVV/
https://github.com/TerryCavanagh/VVVVVV

I reached out to the author about the license, specifically to ask about whether it could be changed to something like CC BY-SA 4.0, as it's easy to understand, extends the freedom of the user of the software, and complies with the DFSG.

The author said that while they acknowledge some shortcomings of the current LICENSE (a custom one that's maybe most similar to CC BY-SA-NC 4.0, and I believe, incompatible with DFSG), they're not looking to change it at this time.

The author does however permit this case-by-case list of exceptions to the LICENSE:
https://github.com/TerryCavanagh/VVVVVV/blob/master/License%20exceptions.md

I believe these exceptions grant distribution of the application binary, as well as the game's proprietary data files. I was wondering if it'd be possible to build the game targeting the non-free section of the repository.

If not, could someone confirm that a change to CC BY-SA 4.0, with an open-licensed set of data files, would comply with DFSG, and thus be able to land in the main section of the repository?

Thanks,
- Ben (computermouth)