I don't see what you're referring to regarding plain language -- would you be so kind as to provide the quote from the document?

The two sentences that lead me to believe that the document applies to all contributors are:

> The founder of SQLite and all current developers have pledged to follow the spirit of The Rule to the best of their ability.

> They view The Rule as their promise to all SQLite users of how the developers are expected to behave.

Granted, it only refers to current developers, but if they view it as a promise for "how the developers are expected to behave", that indicates to me that future contributors would be held to it as a standard.

Of which is their right -- it's their project and they can determine who they want contributions from just as much as any other project. But it lacking any statement to the contrary, it certainly seems like religious belief is one of the bases on which contributors are judged.