There is no nuance. These words mean completely different things. Is there some sort of context you saw them in where they would mean similar things? commit = 1) to make an illegal action, commit a crime. 2) adhere to a specific policy, idea or action, commit oneself to their word. More definitions but these are the most common uses of the word. require = 1) to make a condition upon which another action is based, a license is required to drive, I require your attention.

Committing to something is an act you do of your own volition. Being required to do something is mandatory.