Ive very recently gotten into all the crazy stuff I can do on my modded PSP. So, there is this emulator, called Bochs, that will apparently allow you to run Windows 95 on a PSP, along with, presumably, any applications windows 95 can run. So, can Win95 run DoomRL? That I do not know. I won't be able to try this out for a week or two yet, and I have to figure a way to install Win95 on a spare hard drive, among other things. But, it could work.
Similarly, Bochs can run Linux on a PSP, but unfortunately a lack of keyboard input makes that one temporarily unusable. Windows has minimal mouse emulation or something, and you can use the Virtual keyboard for input, though in-game I don't quite know how that will work either.
Also, if a DOS port of DoomRL were released, theres a Dosbox port for the PSP underway, so it could be run that way.
I don't know if the Nintendo DS offers up any similar OS emulation (I doubt it though), but PSP users take heart, we may yet get some DoomRL portable.
UPDATE:
I succeeded in putting Windows 98 and DoomRL on my PSP, however the game is still unplayable. When I start it, the video goes all wonky and I get vertical pinkish purple bars across the screen along with glimpses of the window bars for the folder containing DoomRL and the application itself. If I hit enter a few times to start the game, I get the blue screen of death. So, perhaps in the future more stable versions of Windows for the PSP will be released (the team is working to get XP running, lol) but until then it just aint playable.
Unless Kornel releases a DOS version, cuz that would run just fine. Hey Kornel, release a DOS version! Well, only if its not too much work. DOS emulation on the PSP is pretty good, though still slow. A soundless version would probly run great though. Theres also some sorta DOS emulator for the DS I believe, so it would possible run on that too.
Well, if its too much work, dont worry bout it, but if it can be done without much effort, a DOS version would actually have a use, and I for one would appreciate it.