Honestly I would be a bit concerned by outsourcing toady got for the game, I think a big part of why it's such an amazing game is because he's not fighting with a team of coders over how to do this or implement that - as a solo developer he can do things the way he feels is best, and keep the game as close to his vision for it as his skill as a coder (and time, etc) allows. The more people get involved, the more compromises he would have to make for the group to function, and the farther from his ideal the game would get. At least with the current development model, fans can give feedback and help improve the game, but it's up to Toady how to handle everything, and what suggestions to listen too, etc. So he can keep an eye on what needs work, while still maintaining control.
As for the possibility of him passing away before it's complete, that is an unfortunate possibility for anything like this, it would be very sad if that were the case, but at least toady has an archive of older version around, and if I recall in the readme file it says redistribution is allowed - meaning if something does happen the community and game can continue in whatever state he left it in at least.
If you really want to help the game thrive and continue, then donate when/if you get a chance, and if you can't do that, try to advertize for him, I've gotten a few people to play and hopefully at least one or two of them will love it enough to make a donation.
><; I need to donate but I currently have no money to spare (student loans are a problem...) but I plan to make a donation if I get any extra cash soon.
Toady is nice enough to offer this amazing game free, despite how much work he's putting into it - I think he's earned the donations.
As for multithreading, the poor guy has so much to do for this game, and trying to make multithreading work properly, on his own (which I think is how he would handle it if he chose too) would probably put progress in most or all other goals of the project on hold for a very long time, If he finds a way to implement it quickly and painlessly, then maybe it would be worthwhile, but as-is I don't see it being a reasonable goal, and I don't think it's something we should expect to see. (not to mention as others have said he basically said "no" to it, lol)