time-pilots-online
This aims to be an multiplayer in-browser game based on the all-time classic Time Pilot. There's a Flash based rendition of the original at http://www.minijuegos.com/Time-Pilot/6983 if you need to see it. The ROM runs fine in MAME if you prefer.
The main difference with the original game would, of course, be the multiplayer part, but maybe some other details can differ from the original.
OTOH something which should most probably be kept is the control scheme. In Time Pilot you can't control speed in any way; it is fixed. You can only turn, left or right, and fire. While this does make the game quite harder to play than some other shmups at first, the mechanics of that kind of movement prevent in themselves some of the potential cheats a client might try. Anyway, this will be further discussed throughout the development.
For now, if you want access to the repository just ask. Pull requests are also fine, of course, but if you plan on helping frequently just ask for commit permission :)