This post on the Gearbox Software forums reveals the company's plans to release Halo Custom Edition, a new version of Halo free for all Halo PC owners. Unsupported by Microsoft, HaloCE will introduce new features to the game including the support of custom content.

So what is the purpose of HaloCE? HaloCE was created as a way for Gearbox to introduce a bunch of new features to HaloPC. The most important of which is the ability to play user created content. Along with HaloCE we will also be releasing a set of tools, tutorials and source art which we call the Halo Editing Kit (HEK). This is a powerful package which will allow users to create their own custom content for HaloCE. When released it is our hope that this new version of the game will become the first choice for all HaloPC players. We look forward to sharing more information with you and answering your questions about this exciting release.