Update:

Black Mesa is complete up to Lamda Core, and so will not include any of the Xen sections from its source material, Half-Life, the developers have announced.

“We believe this is a great way to provide a complete-feeling 8-10 hour experience with a solid ending, make our fans happy and help us make the best overall game possible," said project leader Carlos Montero.

“Development on Xen is already underway and we hope to have it finished up in a reasonable timeframe. Xen is going to basically be a complete game in its own right, it’s not going to be just an epilogue to the game; more of a whole new chapter. It’ll be pretty well expanded.”

Original story:

Black Mesa, the third-party Source Engine remake of Half-Life, will be released on September 14, the developers have announced.

A PC-only release, the game has been worked on by a team of volunteers for over eight years.

It was due for release in 2009 but was delayed because the team were dissatisfied with the way it was shaping up.

Valve itself ported Half-Life over to the Source engine with 2004's Half-Life: Source, although the original game’s textures and models were still used.

Black Mesa will be free to download, and the game’s soundtrack may be purchased for any price the buyer specifies.