When I initially announced the Aura project, it was targeted at PHP 5.3. With a stable release of PHP 5.4 impending, we have moved the target to PHP 5.4. In addition, we have made 1.0.0-beta1 releases of almost all the component packages. (See an earlier announcement from Hari KT.)
The Aura repositories are a collection of high-quality well-tested independent library packages. (Test coverage is 100% at the time of this writing.)
The repositories include such packages as a dependency injection container, a PSR-0 compliant autoloader, command line tools, a data marshaling system, a view system, and a bare-bones web controller. These packages are truly independent: each is self-contained and has no other package dependencies.
Aura also comes with a repository that composes the independent packages into a framework, gluing them together into a cohesive system for project development.