Traditions on homosexuality sometimes go beyond what the law actually says, especially in regard to female homosexuality. We'll be looking at the actual literal wording of the law, surrounding and related passages, and we'll discuss the implications of these commands. Also, we'll discuss the concept of a homosexual lifestyle (including gay marriage).
[Aleksandr Sigalov:] The main reason why woman+woman is not prohibited is because Torah allows polygamy and because women do not have organs to have sexual intercourse with each other. Only HOMOSEXUAL BEHAVIOR is prohibited - not HOMOSEXUAL ORIENTATION. If you like to hang out with guys platonically, Torah does not prohibit that. Only gross stuff like sex and other perverted behavior.
Please see this post for detailed discussion of this subject.