@dulsi: You mentioned Witch Blast, one of your games (a fork): About how many non-commercial files are we talking?
And what did you change from the original Witch Blast? I guess you added Gamerzilla?
I only added Gamerzilla support. All art and sounds are CC-BY-NC-SA. I haven't looked into how many files there are. I like the art style of the game so I would rather contact the creator to relicense it than redo all the graphics. I just haven't tried doing that. I emailed him when modifying Ostrich Riders but haven't reached out since. Ostrich Riders was another of his games.