Legalities of using ZDoom (or other sourceport) for commerce

[darkhog]

It kinda is and as mentioned in the thread it's a license exploit that could be contested in the court of law. Also, this approach would make it impossible to sell the game on Steam due to technicalities related to how Steam downloads and installs games.

[Graf Zahl]

@darkhog:

Nearly all other ports are GPL so what you need depends on what kind of mod you are thinking about.

[maseter]

Do you know of any other source ports that use software renderer and aren't a licensing nightmare?

Why bother with software, when you can have OpenGL, which "performs true 3D projection and does not use Y-shearing"!
That's a must for anyone playing with mouse look enabled, and most do, read: http://zdoom.org/wiki/Y-shearing