Several prominent Mac security researchers have reported that they received invitations to try out the Lion preview, which .

"Apple has invited me to look at the Lion developer preview," said in a tweet yesterday. "I won't be able to comment on it until its release, but hooray for free access!"

is the co-author of .

Charlie Miller, an analyst with Baltimore-based consulting firm Independent Security Evaluators (ISE) and Dai Zovi's co-author, confirmed today that he had also received an invitation to try out Lion.

The preview comes with a non-disclosure agreement (NDA) that prevents Zovi, Miller and others from commenting publicly about what they find. But Apple has asked for feedback and provided researchers an e-mail address to report vulnerabilities or other issues, said Miller.