I like to learn new stuff by doing personal projects, but since there are so many things to learn, I select those that, one day, might benefit me professionally as well: as a consultant, to help me with perform some task at work more efficiently, etc.

Most new languages that gather some kind of following get their start outside a commercial environment.

If a tool has a license so toxic that many companies (1) simply rule out their installation on company servers or company laptops out of principle, I move on and select something else to learn.

> the thing you need

The license makes it so that I'll never know whether I need it or not.

(1) Google is one of them: https://opensource.google/docs/using/agpl-policy/