We surely need some lawyer power here to clarify 
But some more information can be found here:
BTW, it is something completely different if the end user roots his/her phone. That is not illegal and it is even not clear if it voids the warranty in most cases. Some apps will refuse to run and that’s about it. But as a vendor, fairphone will get into legal trouble if it sells a rooted phone with gapps preinstalled. That has always been my understanding.
I would still appreciate an easy way to root my phone. But at least for me, as opposed to the many ppl waiting to restore their backups, I do not need to root it as urgently.
I would have even more appreciated a fairphone without gapps preinstalled and instead having an os with gapps as optional - so exactly the opposite as it is now. But I know that a decision had to be made at some point and I assume that the majority of ppl lives better with gapps preinstalled (see above thread).