I think we’re saying the same thing. The licensing isn’t compulsory, but if ONE CHOOSES to license liberally, those are the terms of use. A benevolent actor could patent a thing, freely license, and head off another actor that would patent-and-lock-down.

It's not necessary to spend the money to obtain a patent in order to prevent others from patenting an invention. All you need to do is make the invention available by publishing it somewhere discoverable by the relevant public. The publication doesn't need to be in an academic journal either. A recent case found that a message on Usenet was sufficiently public because Usenet is organized hierarchically into newsgroups on various topics. A blog post would also probably suffice, so long as it's indexed by a search engine.