Would be interesting to hear your thoughts.
AGPL/GPL:
If you do this people in the community may like this. But you will have problems selling commercial licenses to people. To get around this, many companies do a dual license model where you can get the code under AGPL for free or pay for a commercial license. However, to make this work, you will have to get all your contributors to sign a contributors agreement giving you some rights. Some will hate this and won't.
BSD:
There is a risk that an outside company will take code and profit from it without giving back. Some contributors will avoid because of that. But then, no issues folding community contributions back into your commercial codebase. Contributor Agreement much simpler and less controversial.
I personally went the BSD route for http://ican.openacalendar.org/ - I like simplicity.
Looking at the Opencall website, your are only selling it as a hosted service and not as a product. Both GPL and BSD will allow someone to create a competing hosting service and add any proprietary addition to it without having to share it back. AGPL would make sure that any such addition is shared back, so your business will always has access to improved versions.
Contributor Agreement is irrelevant since you won't need one if you just do hosting.
Given that OpenCall is Open Source, this is very possible.
Good point re diff between on GPL/BSD and AGPL. Tho if I may add, AGPL will only state that in writing. A bad company may break that, and then it's up to how willing you are to get legal on them to enforce the AGPL. Some people may be unwilling to do this, so this may play into the choice of license you go for.
I think the perceived drawback with AGPL is that you'll not have the community jump in as readily as with a more permissive license. And there is a lot of negative talk about the license as a result.
Google for example will talk about how AGPL is "more of a procedural issue than anything else" [1] whereas I believe that it is just in their interest to have permissive open source code that they can use and not share back anything. Very little of the Google infrastructure is shared, but there is no doubt that there is a lot of FOSS code in that infrastructure, or as a basis for the infrastructure, which obviously has moved on (and not been shared).
Google once banned AGPL projects from Google Code, but reversed that in Sept. 2010. Maybe the "threat" from AGPL in changing the culture around open licensing is now perceived so low that they aren't afraid of it anymore.
There are successful AGPL projects like MongoDB[2].
[1] http://www.theregister.co.uk/2011/03/31/google_on_open_sourc... [2] http://www.mongodb.org/about/licensing/
Yes, I do work on a bunch of AGPL licensed software which is used by governments, companies and NGOs.