Please, respect the rules instead of ignoring them, and get your rules straight before thinking your correct.
First of all, I respect the rules.
Second, you can use the content that comes with the game for mapping or other stuff. But no way you can edit it or extract them from the GCF. When you own a game doesn't mean you own the content of the game. That's the official version.
Also it doesn't mean you can't extract them to see how they're made, etc etc...
For example copy pasting the vmts and editing them is normal and I'm sure Valve does like people who create new kinds of .vmts with new settings.
Editing a texture it's ok, but it's a higher level, because you can make a vmt by yourself and be the same as a Valve made vmt. You can't make a texture from scratch and look the same as a valve made texture. Editing a Valve texture made by a texture artist who has spend hours to make it doesn't sound very convenient.
And then a more higher level is editing Valve made maps, or taking content from other maps and copypasting on yours. In this case I would call it stealing.
In short, you're not the owner of Valve files, you can use them but you can't edit them. That's why you can't sell maps or mods. Or be paid for doing one.
It doesn't mean you can't do it, Valve doesn't really care, and it's fine if you do it in a moderated way.
With the exception of the bottom 2 bits, which are explained, the page is not correct. With team fortress 2, you do get some hl2 textures and models. It is not illegal to use them, but they still look really out of place in tf2 and should not be used. However, extracting things from the GCFs, and packing them into a map to redistribute, or just distributing them in any way, is illegal and violates the steam EULA. You can still extract from the GCFs, edit, modify, whatever, but don't give them away.
Oh yeah, I never said you can't use HL2 on TF2. You know why? Because if you buy just TF2 the HL2 CGFs comes with the game. They're distributed with the game, so you can use them. But you can't use CSS on TF2, because CSS CGF doesn't come with TF2. That's the real reason you can use HL2 content in TF2.
We are saying the same thing, I think you didn't understand me.