[syllogism]

I thought about this a lot for my project, a suite of NLP tools.

I decided to go for a dual license. You can use the project under the Affero GPL, or you can buy a commercial license for a fee. The idea is that the GPL'ed version would be unattractive to many companies, and the fee is small.

I still have people interested in contributing to the project, even though they have to sign a contributor's agreement that allows me to license their contributions outside the AGPL.