The development of Black Mesa has sure been interesting. For almost ten years now, the team have gone from making a ambitious mod for Half-Life 2, to a stand alone free title to something even grander. Because today, on the 15th birthday of Half-Life, Team Black Mesa announced that they’ve partnered up with Valve to release a improved full version of the game on Steam that’ll be sold alongside the standard free version we know today.
The free version will be receiving another major update and will also go open source when this new Steam Store version goes live. There’s no date yet, but the new improved Black Mesa will have access to things the current version of their Source engine was not capable of, so expect improvements on things like textures and visuals in general. However, Xen is still way off and won’t be appearing in the game for a while.
[Source]