Please balance my recommendation with that of everyone else that ends up replying, but here are my thoughts.
First, to your points:
1. If there is something unique the code does and you want to nurture the project in the open (e.g. GitHub) this can't hurt. If you just want to dump it and move on, save the work of open sourcing it if there is no audience and you don't want to carry it forward.
Just take the technical and non-technical lessons you learned from this and apply them to the next idea!
2. Hmm, this typically gains traction when the company/person offering the hosting has some expertise that is unique and/or trusted. Also forums are going to be a very hard sell, I don't expect you'd be met with much success here. Open source forum software is abundant as well as commercial solutions so there is a lot of competition and I don't know that much market for this.
3. People don't want to join a project that already puckered out. Adding people will not add energy back to the project if you and your co founder already lost it.
4. Sure, if you can get money for it. People won't appreciate you selling the personal information, but you guys can make that decision.
SUMMARY
In short, #1 and #3 should have been things you did going out of the gate when you first launched, e.g. the WordPress model. You could develop a community of more than just users around your idea.
Tossing a dead product over the wall into the open source community can help if you are Intel ditching MeeGo, but if this is "just another community" code base, I don't know that you are going to get any interest.
If the code is impressive, you could put it on GitHub or your repository of choice merely as a record of big systems you have built if you wanted to apply for a job somewhere in the future and show them something you made.
#2 is a total shift and forums... man that just seems like a long hard road to walk sales-wise if you are doing it as a fallback and are not excited about the idea.
Ultimately motivation, energy and persistence lead to success. It sounds like you two burned out on this already... just move on to the next thing that excites you.
You learned a lot, this wasn't a loss, just leverage it to make yourself even more optimized with the next startup.
That is my 2 cents.