There are a few diehard fans who genuinely do appear to treat it as a religion although, like Buddhism, there is no omnipotent deity involved.
The census thing was part joke and part protest against being asked for our religion at all. The idea of having enough people put it on their census form for it to be officially recognised as a religion was shown to be a myth. Seemingly, it wouldn't have mattered if every person in the UK had put "Jedi" in the religion box, it still wouldn't have had to be deemed a religion.