OSS is one of the few remaining examples of actual public cooperation without a profit motive. Injecting capitalism into it is just going to ruin it.
Having the funding model ("is it sustainable") be a separate concern from the codebase ("what's the best way I can make this library/framework") is a GOOD thing to keep separate, almost like the editorial vs advertisement/sales divide in journalism.
It's also a good test to see whether an individual project is worth turning into a business. If not, it can (and arguably should) just remain someone's pet project, a labor of love rather than another cheap money grab.
I don't want Github to turn into the Android app store, with a bunch of useless apps charging $0.99 for some basic functionality.