I took over RISC OS Doom development from Eddie Edwards in October 1998, and began work on developing what I believed to be the most powerful Doom engine currently available. I'm probably a little short of that still, as there are a number of features that Doom could really do with, mostly fed back from Heretic or Hexen, but it's quite close.
Doom+ (as it is known) is published by R-Comp Interactive who have a licence from ID for the Acorn RISC OS port. There was a lot of argument initially - from myself and others - about how legal such a licence is in the light of the public release of Doom+. This appears to have settled down and there is no question that if you want to make Doom yourself you can get hold of Andreas Dehmel's Doom It Yourself port which requires a little programming skill. Doom+ is a different product and contains no code from Andreas' version. I will not compare the Doom+ and 'DIY' games as that would obviously be biased.
I'm continually developing Doom+ in my spare time, whilst I'm not working on RISC OS itself. There are lots of things I would like to do, but not all of these have yet been implemented. If you do have any suggestions then I'd probably like to know so that I can think about them. Most of the things that people suggest are either mindnumbingly hard or would break lots of things so I'm unlikely to do them, but it's nice (sometimes!) to hear what people think.