From Twin Mac:
Apple has seeded build 8B1027 to Apple Developer Platform owners. This build brings Transition Kit systems up to version 10.4.2, and in-sync with the current released version of Mac OS X.
This build includes new tatics to prevent piracy of Mac OS X. First and foremost, software built with 8B1027 will not run on previous Intel builds. Meaning, software built with 10.4.2 on Intel will not run on the current pirated copies. It is likely Apple will continue this procedure until the final candidate stage of Mac OS X for Intel.
In addition, future updates for Xcode for PowerPC Macs will likely prevent running software on older pre-release Intel builds.
Apple is expected to deploy much stronger TPM checks to final candidate builds, if not already implemented, in order to ensure the release versions of Universal Binary software will not run on non-authentic systems.