Apple has changed its policies. Now, the Beta Seed Program is available for non-delevopers (usign your Apple ID).
Join the OS X Beta Seed Program and help make OS X even better. Install the latest pre-release software, try it out, and submit your feedback.
My personal suggestion is not to subscribe immediatly. First of all I asked myself:
"do you really want to test (unstable) betas on the Mac that you use everyday to work and study?".
I haven't a definite answer yet.