I downloaded it and tried it, and it looks quite usefull to me. It detects your game installations (it supports multiple games like HL2, UT2K4, Q4, D3 and some are yet to be added) and gives you a list of submitted maps and mods for the selected game, which you can download from within the Vapour GUI and it installs that stuff into the appropriate directory for you.
So, no Hammer 4.0 without Steam, but a nice way to distribute and get levels and mods. I like this. ![]()