I saw recently that someone had ported Halo CE to the web and had 1024 players in Blood Gulch.

Probably. There have been dozens of examples of taking old games (Crazy Taxi, Super Monkey Ball, Quake, etc) and making WASM browser equivalents using AI to decompile them just on "Show HN" alone.

They often ship the original assets in a somewhat brazen disregard for basic copyright law even when the games are still for sale on places like GOG though.

Last time I gave that a try (without LLM assistance though) it was really hard as games DirectX calls cannot simply be glued to WebGL so performance was bad.