Well debian categorizes packages so that you can tell what is required. It doesn't really define what the software generally is. The Linux mentality for the term 'Free' generally means that it is freely modified, distributed and available to other programmers. However Freeware is, simply put, just a noncommercial game that you can own free of charge.

I'd call it open source because thats what it is. You're releasing the game with the source code.