Matriculating as master's student just for credits, with the intention of dropping after a year
You know you are planning to drop out, but no one else needs to know.  People's plans change all the time.  For example, a person might start a master's, then realize he actually wants to work toward a PhD.  He might start at one institution or in one program and realize he actually wants to be somewhere else.  If he has done good work before the change, and if he is not someone who habitually starts things but abandons them before finishing... I don't see a red admissions flag here.

I don't see an ethical problem either, because when you start a master's program, you are part of a flock.  The program doesn't suffer if you leave after 2 semesters, and an advisor hasn't invested a lot of time and thought into how to best guide you.

Caveat: I have never sat on an admissions committee.