AGPL all the way. The best way to keep things opensource and have large corporations pay you to use your sofwtare.
It's a perfectly competitive license and fair. If they change your code and offer it as a service, they must publish the changes which will benefit you, the original author. There's also a chance it will require they open source some of their other code as AGPL.
It's the perfect trap and most corporations won't touch it. What constitutes a change is very fuzzy since it covers access over a network.
I would argue that, for a player committed to host an AGPL licensed system, it narrows down to properly fencing the system from proprietary systems.
I personally maintain an AGPL based project but I treat the "lawyers will not touch it" as a case of "security by obscurity".
There's nothing fuzzy about access over the network:
> The GNU Affero General Public License is based on the GNU GPL, but has an additional term to allow users who interact with the licensed software over a network to receive the source for that program. We recommend that people consider using the GNU AGPL for any software which will commonly be run over a network.
http://www.gnu.org/licenses/licenses.html#AGPL
If a corporation hosts an unmodified or even modified version of the AGPL system, where they can afford to share their modifications, they can still leverage their scale / network effect and take the creator out of business.