Would it be considered ethical to publish my own personal notes from class? In addition, is there a change when the class transitions from in session to being complete (at the end of the semester)?
For example when this may be relevant, there are courses where the Professor publishes his slides onto a class portal, but excludes certain material that is only covered in class. This is to incentivize students to show up, rather than only study from the from published slides.
The ethical thing to do, in my opinion, would be to ask the professor's permission.
No, it is not okay and not ethical to do so.
In most cases, a significant portion of your notes will be of copy of what the professor wrote on the board, said orally, or showed via a projector or similar. That means the professor has at least partial authorship to your notes, because he generated the content, even when it is you who wrote the notes down. To illustrate this, it's good to recall that when you want to refer to notes from one of your lectures in a thesis or homework text, you'd usually give the professor's name as author, not your name.
When publishing anything where joint authorship exists, it's a general rule to require permission of all authors. That would include the professor in your case. This is for both ethical and legal reasons. The lecture material is either copyrighted by your professor or by whomever he has it from. What you have is either a copy or a derivative work, and you require the original authors permission to publish that.
