The free-to-play version of Star Wars: The Old Republic will feature a number of limitations.
Star Wars: The Old Republic is going free-to-play, but that doesn't mean that it's just going to fling open the doors to everyone. It costs money to run a game like this, after all, and EA and BioWare aren't doing this out of the goodness of their hearts. That's why, even though you'll be able to fly the Imperial skies at zero cost, you won't be able to do so with quite the same level of comfort and convenience as though who pay for the privilege.
Players taking the free-to-play route will be able to take their characters to level 50, the same as everyone else, but character creation options will be limited. Warzones, Space Missions and Flashpoint Rewards will be limited to three per week unless weekly passes granting unlimited access are purchased, and Operations will require a weekly pass. There will be no access to Emergency Fleet Passes, quick travel will have a longer cooldown period, "purple items" will require the purchase of a license from the Cartel Market in order to be equipped and of course paying players will be given priority status in the login queue.
There are other restrictions to get mad about, which you can discover via the handy-dandy chart now up on the Star Wars: The Old Republic website. It's a bit bare-bones, but BioWare says that more information about free-to-play access is coming soon. No specific date for the free-to-play changeover has been revealed, but it's currently expected to take place "later this fall."
Source: Star Wars: The Old Republic