FreeSynd 0.2 is out! It's not yet mentioned on their site but you can get it from the project download page (Windows only, but 0.1 had a Linux version so hopefully it'll follow soon). I loved the original Syndicate (although the sequel Syndicate Wars was better). What a game that was. I can hardly wait for it to download... downloaded... playing... ok! That was a blast from the past. Only the first mission is playable but it's clear they have gotten through a lot of the harder work on this project. Future versions should be quite fun to play.
However they are using the art & media from the original - I would have thought that is of questionable legality (the game is classed as abandonware) but I can't comment properly without knowing the facts and they are not so easy to come by for a game with so little official documentation online.
Speaking of classic DOS games and open source efforts to revive them, UFO2000 no longer needs data files from the original to play it - a new fan-made set of graphics is included with UFO2000 by default. UFO: Enemy Unknown is probably one of the best games for it's time. Ever.
One of the lesser-known open source real-time strategy games is Dark Oberon. Ubuntu packages have been made for it so maybe now it'll get a bit more exposure. Dark Oberon has a fairly unique approach to graphics design - the images have been created from plasticine models giving the game a very distinctive and original look and feel. However I'm not sure that there is an AI included in the latest release as the roadmap states it has been removed, and it's reinstatement is part of an ongoing reimplementation of most parts of the game.
Speaking of free RTS games, Globulation2 alpha23 was released a week or so ago. The codebase is going to undergo a rewrite before the next release so I imagine alpha23 will be the last release for some time. Rewrites can be deadly for open source projects as a game can be in limbo for the duration of the rewrite and if the rewrite is never completed then the game often stagnates. It's happened to quite a few games over the years. Still the Globulation2 development has been steady for several years so hopefully it will not meet a similar fate.
Woo, all those games have Linux support. I was beginning to get worried I was mentioning far too many Windows only titles lately. ;-)