timppu: So how is that done technically? Some kind of flash-based emulator running the original game's ROMs, or a whole new flash remake of the original game (ie. a port), or something else? I presume they are not streamed to the player?
From one of the game pages:
The Internet Archive is now experimenting with an in-browser emulator that allows you to try software in the archives. Based on the MESS emulation software, this JSMESS (Javascript MESS) player should run in most modern browsers and will map to most keys on your keyboard. Constant improvements are being done to the emulation software and this interface.