Some time ago I asked the Duke3D people if they'd
release the source-code. At that time they
answered "not planned currently".
The build engine is open source. If someone ported that, they'd have a huge head start if and when the Duke 3D specific sources were released, but I don't expect that they will.
For starters, whenever sourcecode is released, you get a bunch of posts from people saying "LOOK! Source code! Someone port this for me because I don't want to learn the skills required to do it myself!" and usually nobody ports it.
Edit: Heh.. just realised who you were... hey if you asked for the sources, yes, you probably WOULD por it :-D