I agree Richard Hipp should be compensated but he explicitly licensed and releases SQLite under a public domain license: https://www.sqlite.org/copyright.html Not Apache, not MIT, not GPL... public domain. You can do almost anything with it and not be beholden to any demands. You can tell people you built your business on SQLite... or not. It's public domain.

That said SQLite has a business model of selling support and premium features like encryption: https://www.sqlite.org/prosupport.html