How do people learn about licenses?

If you entered into software in a certain way, it's easy to assume that everyone is a part-time license attorney. But how do other people pick up license knowledge? And what does one really need to know?

Licenses underpin open source but seem kind of dull. But they are also a cool and special thing about the software industry.

Lars provides his licenses 101 thoughts and looks forward to becoming open source grandpa.