As of yesterday, Star Wars: The Old Republic is free-to-play for new players until they hit level 15.
The free trial, which EA and Lucasarts announced at E3 last month, is available to anyone who has never set up an active SWTOR account, including players who've played the game using past free trials.
Given the level cap, the free-to-play section is essentially limited to the opening "Origin World" missions for each character class. Trial players also have access to PvP, warzones, and co-operative flashpoint areas.
Bioware has said they're investigating whether or not to make Star Wars: The Old Republic free to play, citing the need to "be flexible and adapt to what is going on." Current players and new players over level 15 must pay 14.99 per month subscription to keep their account active.