Open source is a business tool. There are many business models where open source can be useful. PG has such a vibrant user _and_ developer community that it pays to be a freelancer in that community and there's room for lots to play. SQLite3 is very much the opposite: it has _no_ developer community outside the core team, but the business model is the SQLite Consortium, which pays for the core team, and the closed-source test suite whose existence prevents hard forks.

It makes sense to use attractive-to-end-users licensing at first and later switch to a license that helps lock in support bucks. Call it bait-n-switch if you like, but even the SQLite folks did it, only they didn't do it with the _license_ but with the _test suite_ -- either way they made it really difficult to play in their space and/or fork.