There was just an article in a magazine called "Gamestar" about abandonware and another one about fan projects.

They wrote that fan projects can be closed at all time (and they do especially if a brand still is in use). Sometimes they close their eyes but can stop such a project at every time. They mentioned a lot of examples where this happened. But sometimes a fan project survives (if the brand is almost dead).

A HL2 or other game modification is another story but still similar. Did you ever read the license of such games? Here is an example: If you make a modification for Enemy Territory - Quake Wars then every material that you put into this project automatically becomes a property of the original owners of this game. So all your textures and models become property of Atari as an example. They can stop your project, they can even sell it as their own and dont have to share the profit with you. All that would be possible.

This is the reason why I dont dare to render my models and textures in such game engines. The risk is simply too high.

But if you dont care and you do it only for the fame - then just continue.