You might be looking for "free" community-made DLC or mods that add features to your existing game download.
Keep an eye on the Epic Games Store , which gives away free games weekly. While this specific title hasn't been featured yet, it is the only source for permanent, 100% free legal copies. Alternative Interpretations Terminator: Resistance Free Game Download Full
The game has frequently been part of the Sony subscription catalog. If you have an active membership, you can download the full game at no extra cost. You might be looking for "free" community-made DLC