Hosting Discourse
I haven't used any of these services, so I can't really add any useful experience or informed judgement.
From looking at the links and the discussion on the mailing list, it seems Discourse is the best option based on its rich feature set and flexibility.
It may be difficult to get a uni to host it, because the administrators will want control of it, which makes extra work for them without any connection to a paying project.
I have a server from which I run a couple of websites, include the String Theory Wiki ( http://www.stringwiki.org/ - it's just celebrated it's 10th birthday), from which I wouldn't mind hosting the Discourse site. It would have to use an external mail server.
However I can totally understand if the community would not want its infrastructure concentrated in one person's hands. There would also be limits on how much time I could spend doing admin - the installation looks fine, but if I have to go hacking in Ruby on a regular basis, that's too much.
- Here's a test version of Discourse I installed on my server:
http://discourse.nworbmot.org/
I'll delete this instance soon, it's just to get a feeling for how it works.
Actually, having used it a bit, I find the performance unacceptably slow. It's running on a Virtual Machine with only 1 GB RAM, which is fine for a wiki, but doesn't seem to be enough for Discourse.
So, if we're going to run our own Discourse, it will have to be a bigger, better machine.