The deal is that once you downloaded the game you own it. No need to buy the game again should you want to continue playing. Of course that is unlikely. From what I hear the Planetside servers are almost deserted. As fun as the game is to begin with it doesn’t have the replay value to go on and on for months. The fee is a little steep as well. I bet they would do anything to populate the virtual world and gain potential customers.
For the trial there is a fine print of course:
Important Note: You will be required to enter a valid credit card number and have Windows XP installed to play the free trial. After the 30-day trial period ends, and unless you cancel your trial subscription before the end of the 30-day trial period, Sony Online Entertainment® will begin to charge your credit card on a monthly basis.
Also the download is about 1400 MB and I can imagine the servers are clogged up. Hopefully someone will post this to Suprnova or something just like last time there was a trial.