Our portfolio company 10gen has released the core of its MongoDB database under the GNU Affero General Public License (the drivers are licensed under Apache). Some people react to the Affero GPL by saying something along the lines of “that’s a new license which I don’t want to understand or bother with." I have some sympathy for that initial reaction (who wants to figure out legal stuff), but most of the same people would happily use GPL licensed code without checking whether it is v2 or v3. ...