Just like with a mature person, there is a great deal of knowledge and craft embedded in Solar, but it also still shows its roots and carries the weight of decisions from early in its life. With all that in mind, it's time to start working on Solar version two, using the formal namespaces and other features of PHP 5.3. There are some other very significant changes on the way as well.
The biggest, most obvious change in the project has been the name - Aura. The second is a structure change - Solar's classes all descended from a base class where Aura's structure is more about independent library packages (more along the lines of the Zend Framework's components) with a "system" package to tie them all together. You can find the current codebase on github.