I expect the site should get more activity now that the Steam CSGO workshop is up. Still hard for me to fathom source being out since HL2, which came out in 2004 I believe. 9 years feels like eternity for a game engine.
To put it in perspective, Unreal was on 2.0 when HL2 released. A couple years later we get Unreal Engine 3, then 3.5 with the UDK, and 4 on the horizon. Source still has some life left in it but man, we could really use Half-Life 3 on Source 2 soon haha!