SQLite is open-source, meaning that you can make as many copies of it as you want and do whatever you want with those copies, without limitation. But SQLite is not open-contribution. In order to keep SQLite in the public domain and ensure that the code does not become contaminated with proprietary or licensed content, the project does not accept patches from unknown persons.
All of the code in SQLite is original, having been written specifically for use by SQLite. No code has been copied from unknown sources on the internet.
This model probably won’t work for most projects, but is interesting and seems to be working for this project.
SQLite is one of my favorite examples of dual licensing, because it’s so weird. Usually dual licensing companies choose a license with rules, like copyleft or noncommercial use, and charge for the privilege of breaking those rules. Far as I can tell, SQLite mostly sells licenses to companies that either have legal departments wary of public domain dedications, or software approval processes that require having “a license”.
IIRC, their paid licenses also come with warranties about having the legal rights to license the software. That idea’s constant in proprietary software licensing, but with the partial exception of the Open Software License and Academic Free License, totally absent from open source terms.
Yeah, the SQLite blessing is a charming little thing that I wish more software would draw inspiration from. SQLite in general is a highly idiosyncratic project, and that’s not always for the best (the code of conduct kerfuffle, for example, was well-intended but not handled optimally) but it’s nice to see some heterodoxy in the open source maintenance world.