The Japanese version, of course.
You can register here and pray for your luck. The registration itself is open until 17.01.2012. The testing is supposed to start near the end of January 2012.
If you've registered for the PSO Magazine some time ago, you don't have to do anything.
People who took part in the first alpha test will be accepted automatically.
One more thing - people who get at least 1 character to level 10 during the second alpha test, will be invited to the closed beta.
Just download and install this
It wants a Japanese-enabled browser, dunno what that's about.