My friend and I go to an “all you can eat” buffet. My friend pays for the buffet and fills his plate. He gives me a few things from his plate for me to taste. Since I didn’t pay for the buffet, did I steal, and did my friend violate any halachot if he shares his plate with me?
If when your friend took the food he was intending for himself alone to eat, it is permitted for you to taste from his plate.
It would not be permitted for him to take initially with intention of giving to others.
This assumes that there are no clear in-house relating to this matter.