A few minutes following the release of iOS 8 beta 5, Apple also posted OS X 10.10 Yosemite Developer Preview 5. The build number is stamped 14A283o and now available in both the Dev Center, and the Mac App Store.
A preliminary version of Yosemite available for download from the beginning of June. As you know, since April OS X testing program is open to all comers. Therefore, users who want to install on their computers beta desktop operating system Apple, do not necessarily get official developer account. The “OS X Beta Seed Program” are available to who ever wanting to testing the OS X beta version.