Its heavily (95%+) personal time donation from devs and users who try/test and give feedback. We're mostly working for free, or for some grant funds after applying and being for approved for such. There are a few VC funded projects.

Peoples opinions will differ on whether clients/products/services should be profitable, or even use other traditional revenue streams such as advertising. Im in favor of both, if done well with a positive experience for the user in mind