Google just invited another round of developers to purchase Google Glass. According to Engadget, some developers who previously expressed interest in the high-tech eyewear are now getting invites to become part of the company's Explorer program.

Google is also rolling out a preview of its SDK and opening up Mirror API to developers and are giving anyone who wants to create apps for the high-tech specs an opportunity to do so.

"When you asked us how to get Glass on this site, we told you there would be more chances to join the Explorer Program ... someday. Well, today's the day," the email read. "The sneak peek of the Glass Developer Kit (GDK) is available now, making it possible to build new and innovative kinds of Glassware. We're now inviting you, as a developer, to purchase Glass, become an Explorer and join us in taking the next step in developing for Glass."