Amazing that they seem to have decided to just put that stuff out. And why not, it's been decades for a sizable portions of those. Whatever "we cannot let pre-release demos of Half Life escape because it might tarnish the brand/release" sentiment there might have been does, long since not apply anymore. But a lot of other companies would not bother to update their policies, or even going as far as actively "release" those artifacts.

Kudos, a good day for preservation.