There is no free trial available, but I believe you get 2 keys when you purchase the game (which can be as low as $40)
The second key is a buddy pass that is usually packaged with the game, which is a full game key, just like the regular one.
Once you have your key, the game is currently free to play, untill the SE devs have made a proper plan to progress with updates and fixes.
This is true if you find and un-purchased collectors edition. Game Key + Buddy pass key (2keys in 1 box) http://www.gamestop.com/Catalog/ProductDetails.aspx?product_id=78364
For the standard edition there is no buddy pass, meaning only 1 key. http://www.gamestop.com/Catalog/ProductDetails.aspx?product_id=77288
(Unless you have a Spouse/Significant other/Sibling/or Friend that is need of a code also - the std edition is a better deal for 30$ @ gamestop)