All one has to do to be able to join a Masonic lodge is to be of good character and profess belief in 'a creator'.Bhuddists are allowed. I have some Bhuddist brothers in my lodge.
Hindus are allowed as well, although they are not polytheistic in the way I believe you are thinking. All those deities that Hindus pay hommage to are different manifestations of a single creator.
(That's probably a gross over-oversimplification. If there are any Hindus reading this, I would appreciate some info.)
What deity do they think buddhists believe to be the creator?