If you're an evil dictator with designs on world domination, and want the best database software to build your SDPMS (Superhero Death Plot Management Software), and if you also have an irrational (for an evil dictator) desire to remain compliant with copyright law, where do you go for software?
Free and open source, natch. By definition, free and open source software can't contain any restrictions on use of software for planning global kitten death, transmitting Jim Davidson stand-up routines or developing personal nuclear devices, whereas proprietary software licences commonly do (although rarely with this degree of specificity, except possibly for the nuclear one).
Software is only free if you have complete freedom to run it for any purpose (including evil ones) (freedom zero of the FSF four freedoms). Open source software must not discriminate "against fields of endeavour" (even if the field of endeavour includes annihilation of every life form on the planet).
Licences which attempt to restrict evil (like the JSON licence) are not free, nor are they open source.
Free and open source has a reputation for being associated with wholesome fluffy goodness. Don't be deceived: Dr Evil would use nothing else. You know it makes sense.