If an rh+ baby needs a blood transfusion, can he accept blood from both rh+ and rh- people?

Needs cross match: Yes. (+) blood type can receive either (+) or (-) blood type; negative (-) blood type person can only get (-) blood. But, the "letter" part of blood type also matters. For example, type o should only get type o blood. Unless a blood transfusion is absolutely emergent, a cross match should be done before the blood is transfused.

Yes, if rest OK.: An rh+ baby can get blood from rh+ or rh- people as long as the main type (a, b, o, etc.) matches up, and there are no other antibodies, like kidd, duffy, lewis, etc. Unaccounted for. Conversely, an rh- person, like a childbearing female cannnot/should not get rh+ blood since it could sensitize her and result in hemolytic disease in the newborn if she has an rh+ baby afterwards.