Concept of "gods" in Vajrayana Buddhism As I know Vajrayana Buddhism has a concept of "Gods": it's kind of "polytheism".

How does it related to the concept of non-theism in common "original" Buddhism?
In Tibetan Buddhism, a God is merely a sentient being that is subject to suffering. Gods have afflictions such as ignorance, anger, attachment and so forth. They have mistaken consciousnesses, and so forth. It is just a type of rebirth. You yourself could be reborn as a God. A god is empty of being permanent, unitary, independent, self-sufficient substantially existent, and according to some schools of Tenets empty of true existence as well, and to others empty of inherent existence as well.

So, 'a god' is just a name referring to a type of being that experiences pleasant feelings for a very long time, before he dies and gets reborn as... maybe a human, or a preta, or a hell being, or an animal or a god again.

There is also the concept of 'deity' but that is another matter that is related to secret mantra and the four bodies of a buddha. Basically, a deity is an emanation or a supreme emanation body which is not a being.