For programmers who are curious about OpenMeeting, I've set up a mockup server on my PC. It's is not entirely stock install, I've changed a few configurations to make it more like what we want. No source code changing yet though. You can have a look at it here:
http://forecast.student.utwente.nl:5080/openmeetings/
Go there, wait for a few seconds for it to load, make an account (no verification or anything required), and then you can join the public room. You'll get a popup for video settings: it shows a black screen initially, even though your cam does work when you hit "Start recording test". I've notified the devs that this is very non-intuitive, and they'll be changing it.
Instead of joining the public room, you also have the option to make personal rooms, and invite people in with a link.

My impression about OpenMeetings:
Pros:

• Open source
• Very customizable, because it's open source
• Doesn't require a google account
• It's in active development, with an active mailing list on which people reply quickly
• Easy to limit rooms, get a room overview, and create new rooms

Cons:

• I find the documentation not very intuitive
• It needs a server to run on
• Screensharing is a bit clunky: You can't really use it instead of your webcam, as in google hangout. Should be fine for 1-on-1 video chats though.

Compared to Google hangouts:
Pros:

• Easy to set up
• Doesn't need a server
• Supports screensharing
• Somewhat customizable: It supports widgets, but I'm not sure to what degree the layout is editable.

Cons:

• Needs a google account
• Permanent rooms are a bit of a hack (by creating an event far in the future)

Neither is a clear winner. I'll personally be looking at if it's easy to change the layout on OpenMeetings. If that's doable, then it's already at or beyond the "baseline" level we have with Tinychat.