Matt Walsh (QuakeC, sound and general design):

I had to sue the publisher, Quantum Axcess to get most of my royalties. I went through three lawyers before I found one who followed through with it. The first wanted a description of what we did. Well for the heck of it, I made a video of me playing Shrak, and sent it along with This Letter

we were continually paranoid about id suing us. In fact, because Quake levels had the actual textures compiled into them (which constitutes a copyrighted work) we found a guy who wrote the safetex program. With it, we shipped levels with no textures on them (they looked flat gray) then had a post-install procedure to rip textures from the already-installed original quake levels and paste them into ours. Actually, we first tried to just make all of our own textures, but unfortunately the artist didn't test them outside of photoshop and hence they looked terrible and hence we threw them away.

Source: http://www.mattwalsh.com/twiki/bin/view/Main/ShrakProject