"How manny isnt a diffecult question is it?"
It is, because there is not an exact answer.
I could say only one nick is allowed (would be an ideal situation), then you start to ask why are there so many players with multiple nicks.
Why?
Because on a site which allows free registration, it is not really possible technically to limit the number of registration per user.
Even if we allow only one, there will be thousands of new nicks daily, and it is not really possible to check one by one if they already have an existing nick. (not to speak about the fact that sometimes it is not possible to tell even after thorough investigation).
Therefore, it is generally (unofficially) accepted to create one or two more nicks, meaning you will not get banned for it.
However, if it comes to our attention that someone is using multiple nicks for questionable purposes, or simply is creating an abnormal amount of nicks, it will not be tolerated.
All in all, I can say, what our "Terms of Service" say:
"FlyOrDie reserves the right to restrict access for users who ... register multiple Accounts."
I hope this answers your question.