Yeah, it shouldn't be confusing! We extended early backer pricing for the whole Kickstarter, so the Personal / SMB license would have been $40.

Only difference is who can use the license. Student license is for students only. But I'm recommending students just get the full Personal / SMB license since it's more flexible in the end and a better price.

(Non-profits should ABSOLUTELY get the Student / NP license as it's good for any organization size and just $20).

Students eventually stop being students (i.e. graduate), so doesn't that conflict with the licenses being perpetual?

They can always gift it to another student. :)