Sublime is a set of components, primarily built on top of Symfony2, that aim to faciliate the rapid development of PHP-based web applications.
Sublime's first incarnation was primarily built on the idea that the most important aspect of any framework is what value you can get out of it. It worked quite well and has been deployed in several applications Sublime Labs has built.
After using Symfony2 for a short time, and seeing just how easy it is to integrate well-tested, well-supported code into any application built with it, Sublime started being rewritten.
Originally, this was simply supposed to be switching over to using HttpFoundation for request and response abstraction; However, after taking a look at Silex and other microframeworks, it became clear that more could be done, and with small amounts of custom code we could build something that truly fits our own needs.
We're releasing Sublime in the hopes that someone may eventually find it useful other than ourselves. Due to the nature of the "framework", you could easily build something yourself using the exact same components. If anything, it serves as an example of how easy it is to create a custom framework on top of Symfony2.
Sublime is currently being (mostly) re-written and re-architected from the original Sublime Framework.
Symfony2 Components - HttpKernel, HttpFoundation, EventDispatcher, Routing