Having students scribe lectures: can the instructor choose any license?
I'd ask the students to transfer any copyright to me, formally if need be. In any case, the scribe is writing down what you are writing on the board, so the contents is morally yours in any case.

Presumably the result will undergo wide edition by you, so this is mostly moot.

[A student did transcribe my scribblings a while back; some things  got misunderstood or I plainly messed up, a lot of cleanup was needed, and for the next version I added several examples and clarifications.]