For what reason should one focus on that? I don't see what difference it'd make even if they used the original engine, technical issues aside.

My point wasn't that it would make a difference from a technical standpoint, but that the licenses for the code are/would be different between them and what may apply to one may not apply to the other. Personally I don't see it being a cause for concern, but something to keep in mind anyway, given that unless they develop something that they absolutely cannot make open-source (not impossible to fathom) they'd have to comply with the GPL either way or risk walking through a nightmare for not respecting it (with regard to Wrath, I should mention - I haven't read up on whether Voidpoint intends to make Ion Fury's code open or not though I suspect they will given that it's most of the EDuke devs involved in it).

Well most of the time source ports will inherit and continue to use the original license from the original source release of the original engine. Unfortunately it doesn't always go that way because some people just want to introduce proprietary components or go against the grain...

And in this case, yes, Darkplaces does use the same GPLv2 which is what the Quake engine was eventually released under (in 1999, IIRC).

EDuke32 is a bit more complicated, and I think it's actually illegal to redistribute unless you either remove the GPL parts from it or remove the BUILD parts from it. If you do the former, you also need Silverman's permission for a commercial release... sigh.