Comment 8 for bug 268397

I suspected that the upstream notice refers to the non-free music and sounds, but it can't hurt to be certain.

The licensing FAQ[1] of upstream states the following:

"All source code found on this site is available under the GNU General Public License (often referred to as the GPL). You can obtain a copy of the license by clicking here [link to GPLv2]."

"Please make sure you are aware of the terms of this license before installing or running our software. Please also note that game assets are Non Free and should not be included as part of a Linux distribution or made available in any repositories."

This is more clear than "This game should not be added to Linux distributions or respositories." And it does seem to also suggest that the non-free data is the only problem. According to Wikipedia[2], "artwork (including textures and 3D models), sound effects and music, text, dialogue" are game assets.

Note that there might be other non-free data besides just music and sounds; only source code is released under GPL.

I have already emailed upstream and received an inconclusive response. After replying and making my request more specific, I am waiting for a response. I have attached the correspondence. I will keep you updated with any response(s).

[1] http://www.parallelrealities.co.uk/faqs.php#License%20FAQ
[2] http://en.wikipedia.org/wiki/Game_development#Duration