The latest build is dubbed 11C57 and it is about a 740MB download in its delta form, according to people familiar with the software. The latest build is said to have no known issues.
As with the previous build released on Sunday, the latest version is said to include iCloud in the installer. Previously, developers had to download and install iCloud separately for testing.
Apple also began transitioning user accounts from MobileMe to iCloud this past weekend. That allows developers to transfer mail, contacts and calendars to the new iCloud.com site.
Also like the earlier build, the focus areas Apple has asked developers to concentrate on in Friday's latest update reportedly include the new iCloud, as well as Address Book, iCal, Mail, MobileMe, and Safari.
This fall's launch of iCloud will come with the Lion update, as well as a new version of iTunes. Beta release of the new iTunes 10.5 have also been supplied to developers for testing, along with pre-release versions of iWork for iOS.