How are companies or developers supposed to make a full time living with OSI opensourced projects?

There has been a lot of talk about companies and individuals adopting licenses that aren't OSI opensource to protect themselves from mega-corp leechers. Developers have also been condemned who put donation notices in the command-line or during package installation. Projects with opensource cores and paid extensions have also been targets of vitriol.

So, let's say we wanted to make it possible for the majority of developers to work on software that strictly follows the definition of opensource, which models would be acceptable to make enough money to work on those projects full-time?