English original text is: 'A person may be an initiate of more than one cult, so long as he maintains all the requirements (including tithing and time) for all his cults. None of this cults may be hostile or unfriendly to another.'
That means 1) that your back translation from french is ok and2) that neutral cults are (or more properly were) compatible. This clearly contradicts RQ2 statement, as expressed by Jeff, but also contradicts Jeff that situation has not changed. The problem I see is that RQ3's matrix is about pantheons and not individual cults.
On this, I fully agree.
If I stay with RQ3's ruling, I agree, because neutral cults may have compatible beliefs and world views, but I can't see hostile or enemy cults being compatible, even if with exactly the same beliefs.