Community Manager Rick Heaton announced the lift on the forums: "Today we have officially released Riders of Rohan beta testers from their NDA. Beta testing will continue as we move towards our new release date of October 15th. In the meantime, those beta testers who wish to share their thoughts and experiences thus far with the general community are encouraged to do so here."
With the NDA lift comes news that Turbine has been secretly working on a native OSX client for Mac players. It remains to be seen whether or not this client will be available with Riders of Rohan's launch.