Wikipedia
Widelands
Widelands is a free slow-paced real-time strategy video game under the GNU General Public License. Widelands takes many ideas from and is quite similar to The Settlers and The Settlers II. It is still a work in progress game, with development still required in graphics and bugfixing. The game runs on several operating systems such as AmigaOS 4, Linux, BSD, Mac OS X and Windows.