https://store.steampowered.com/news/57848/ Bit late for this news, but I know some of you guys like your Half Life. Go and experience any of the series yourself... or join a server and do these kind of stuff. 8 more days to enjoy these free~ After that, it'll be snapped away. Unless you bought em of course.
Essentially, yes. You can still do stuff with it like you own it such as Multiplayer... but after 8 days. That's it. There are other permanent free games on Steam if you look around. Like Tomb Raider : https://store.steampowered.com/app/203160/Tomb_Raider/ I remember buying a disk for this, now I can own it on Steam.