Is it okay liking your boyfriend's best friend?

Anyone can like anyone. Like involves no commitment and is often very transient. For example a mother may love her child without question, but only like that child for short periods depending on the child's behaviour. Love requires a commitment to another person and true love always gives itself to its object, regardless of consequences.

It is okay to like your boyfriend's best friend, if only you don't fall in love with him, since it would ruin the friendship of your boyfriend and his friend and/or ruin the relationship between you and your boyfriend.