IANAL - but this seems a reasonable license to use for something that will mostly run on servers. Specifically quoting from Why the Affero GPL:
The GNU Affero General Public License is a modified version of the ordinary GNU GPL version 3. It has one added requirement: if you run the program on a server and let other users communicate with it there, your server must also allow them to download the source code corresponding to the program that it’s running. If what’s running there is your modified version of the program, the server’s users must get the source code as you modified it.
The content of the new license was taken directly from http://www.gnu.org/licenses/agpl-3.0.txt
PS see also http://cl.ly/5nAo - we’re in Peanut Butter Hula Hoops territory now