It appears that the community is down to it's core members and newcomers are rare, good ones being another brand of rare. If you know what you're doing and if you're able to make some creditable progress by yourself, I reckon you might get people interested in your project and recruit some helpers.
So yeah, I'd say that the community is still active, it may be a crummy fraction of something like the Half-Life 2 modding community in terms of size, but it's not dead at all and there are several quite talented individuals here.
Things seem to go at a slowy pace too, so it doesn't really matter if the work you're going to put in your mod will be occasional.
My advice to you is that if you're confident you can start something good by all means give it a try.
Thank you for your interested in my work MT, but I cannot take much participation in any other mod since I'm already working in Doom Desire, which is quite a big project itself.
I can do small jobs for a good mod who needs it once in a while but that's about it.