Old Versions of Valve Games As A Mods is a project that aimed to recreate old good games at different development stages after their releases. They are based on extracted content from old gcf files and fixed as it possible to run as Source SDK mods.
Update # 1.
How to install old version of Half-Life 2 (01.10.2010) as a mod tutorial is done.http://www.moddb.com/mods/old-versions-of-valve-games-as-mods/tutorials/how-to-install-half-life-2-01102010
Update # 2
How to install old version of Half-Life 2: Episode One (...10.06.2011) as a mod tutorial is done.http://www.moddb.com/mods/old-versions-of-valve-games-as-mods/tutorials/how-to-install-old-version-of-half-life-2-episode-one-10062011-as-a-modhttp://media.moddb.com/images/mods/1/23/22739/01.jpghttp://media.moddb.com/images/mods/1/23/22739/02.jpghttp://media.moddb.com/images/mods/1/23/22739/03.jpghttp://media.moddb.com/images/mods/1/23/22739/04.jpghttp://media.moddb.com/images/mods/1/23/22739/05.jpg
Q: Is it illegal?
A: No. Illegal is only "bin" folder and "hl2.exe" file. Folders kinda "hl2", "episodic", "cstrike", "ep2", "portal" is not illegal. Mods uses only game content folders.
Here's the proof that shows how people can distribute files to run old broken HL2 mods as Source SDK HL2 mods:http://forums.steampowered.com/forums/showthread.php?t=1289845
These mods have the same structure.
Q: Do these mods need original games?
A: Yes. "Half-Life 2 (01.10.2010)" needs original Half-Life 2 and Source SDK Base 2006:http://www.moddb.com/mods/old-versions-of-valve-games-as-mods/tutorials/how-to-install-half-life-2-01102010
"3) Install Half-Life 2 (Library => All Games => Half-Life 2 => Install Game). Not needed if it already installed.
4) Validate Half-Life 2 (Library => All Games => Half-Life 2 => Install Game => Local Files =>Verify Integrity of game cache). Not needed if it already validated.
5) Install Source SDK Base 2006 (Library => Tools => Source SDK Base 2006 => Install Game).
6) Validate Source SDK Base 2006 (Library => Tools => Source SDK Base 2006 => Local Files =>Verify Integrity of tool cache)."