Fileplanet started their open beta key giveaway promotion but there seems to be some problems. Apparently the first batch of keys they gave away was wrong. NCSOFT German community representative (and later on Lani) said the following:
Fileplanet had wrong keys but will send out NA #Aion Open Beta keys to everyone who received a wrong key again.
In any case – if you are in North America you should go to this Fileplanet page and grab your key asap. I don’t think you need the paid subscription but it is first come first served basis so hurry up.
All you have to do is an email with the subject “Atreia” to the email address to write email@example.com too