https://steamcommunity.com/sharedfiles/filedetails/?id=96730733&insideModal=1
and bit closer
https://steamcommunity.com/sharedfiles/filedetails/?id=96730690&insideModal=1
Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.