The definition of religion is 'a strong belief in a supernatural power or powers that control human destiny'. Since science isn't 'supernatural', I don't see how it could ever be regarded as a religion.
Well I supose you could have Spinozas, Naturalistic, or Scientific Pantheism. Which replaces 'supernatural' with 'natural', although the use of the word pantheism causes some consternation among non-religioinists.
I think Buddhism allows one not to believe in God, if that makes sense.
You can be a Buddhist and believe in God or you can be a Buddhist and not believe in God, up to you.
Whilst we in general think of religion as belief in the supernatural , one of the definitions is : ' A cause, principle,or system of beliefs held to with ardor and faith ' therefore Communism although atheistic can be termed a religion.