Can you switch military branches if you have an administrative separation?

My husband is a marine, and in the last year of his contract. He was interested in switching branches to the Army when his contract was finished, but he may be processed out sooner than that for weight control. Because it's not a dishonorable discharge, would he still be eligible to switch branches? My sister is in the Army NG and says the NG will probably take him as long as the discharge is not dishonorable and if he can show that he can meet their height/weight standard. Is it the same for active duty?