It should be obvious why, but if not consider a future where the SQLite team needs to replace a member. What's the plan if the best candidate is an Orthodox Jew? Are they going to update the CoE to read:
>The founder of SQLite and all current developers, except for Ruth Cohen, have pledged...
Even if they're the nicest and most welcoming Christians in the world and will make a better change without hesitation it's still presents a disincentive for non-Christians. There's simply no place for that in any professional setting.