A_Future_Pilot: However Rebirth's code was just recently changed over to GPLv3 just fyi. I don't know if that includes the paralax code or not (I'm under the impression it does.)
A dangerous impression created by the horrible intricacies of GPLv3. Only the DXX Rebirth Team's _original_ code (not derived from the Paralax code) is GPLv3. Paralax' code remains proprietary and is easy to spot by comparison to the original. But also, derivative code by the DXX Rebirth Team is under Paralax' terms. This is harder to spot. The DXX Rebirth Team code might look totally different from Paralax' but in fact been derivative rather than Team original. GPLv1 & GPLv2 did not allow license mixtures, but GPLv3 does. The effect is, GPLv3 code can be placed under every restriction of any proprietary code it is mixed with.
Compare to Doom. Users can download the Doom engine with no legal entanglements beyond granting others the same right they themselves received. Then they can download the freedoom content (freedoom is a single player game providing an equivalent to the original Doom experience), and other non-proprietary multiplayer levels, no cost, no entanglements. A totally free as in freedom experience. But, despite a multitude of non-proprietary single and multiplayer levels for Descent, _any_ experience users seek will bind them to Paralax' proprietary restrictions. The use of "GPL" by the DXX Rebirth project does absolutely nothing for freedom.