Then again, I am used to being the sole programmer in my projects.
Did you ever happen to be in the situation where your project used to work great two days ago but now doesn't? You are screwed without a versioning system, even if you develop the project alone. And as soon as you have 2 programmers, you don't ever want to look back.
With TortoiseHG, don't forget extensions like rebase/translate though (okay, the former only if you are coming from a git background -.-)
I personally like the idea of hosting Horde3D at the university's server
If that would work, that would be the perfect solution.
Oh, and btw: The decentralized nature of Mercurial would imply, that you don't need to finally choose now - you can move your complete repository somewhere else, without ANY problems. So go with the best that is there now, and the switch as soon as there is something better. BerliOS looks good so far.
EDIT: Btw, any opinion about my suggestion to split the repository, one without and one with all extensions?
EDIT2: IRC ftw for such discussions ;D