Stratagus

Stratagus is a free and open-source cross-platform game engine used to build real-time strategy video games. Licensed under the GNU GPL-2.0-only, it is written mostly in C++ with the configuration language being Lua.
History.
On June 15, 1998 Lutz Sammer released the first public version of a free "Warcraft II" clone for Linux he had written, named "ALE Clone". In 1999 it was renamed to "Freecraft". In June 2003, a cease and desist letter was received from Blizzard Entertainment, who thought the name "Freecraft" could cause confusion with the names "StarCraft" and "Warcraft", and that some of the ideas within the engine were too similar to "Warcraft II". The project halted on June 20, 2003.
The developers regrouped in 2004 to continue work on the project, renaming it "Stratagus". Their focus changed from cloning "Warcraft II" to creating an open source, configurable engine for RTS games including support for playing over Internet/LAN or playing vs. computer opponents. A separate project, "Wargus", was started to get "Warcraft II" data files running in the "Stratagus" engine. This mod requires a legal copy of "Warcraft II" and allows for cross-platform support such as Linux and other operating systems. The free media set imitating "Warcraft II" was discontinued.
On June 10, 2007, development of Stratagus was paused.
The "Stratagus" developers began working on "Bos Wars", which uses its own modified version of the "Stratagus" engine.
In June 2010 some of the developers moved "Stratagus" project from Sourceforge to Launchpad and started working on "Stratagus" and games again. "Wargus" (for Warcraft II), "War1gus" (for "Warcraft I") and "Stargus" (for "Starcraft") continued to be developed by the Stratagus team on Launchpad. In 2014, Wyrmgus started as a fork from the "Stratagus" engine to develop a strategy game based on free assets with a wider scope than the original engine allowed. The "Stratagus" team has since also moved to GitHub.
Playable "Stratagus"-based games are: fantasy "Aleona's Tales", medieval "Battle for Mandicor", "Warcraft II: Tides of Darkness" (plus expansion "Beyond the Dark Portal") port "Wargus", "Warcraft: Orcs and Humans" port "War1gus", futuristic "Battle of Survival", historically-inspired "Commander Stalin", "StarCraft" port "Stargus", and space age "Astroseries". Of these, only "Aleona's Tales", "Wargus", "War1gus", and "Wyrmsun" are complete.
Programming.
The "Stratagus engine" is a 2D engine based on cross-platform open-source libraries like SDL, gzip, bzip2 and others.
Basing on Lua as their primary scripting language, virtually all the abilities in the engine have been made available to the users of Stratagus for easy modding, removing the need to change the original C/C++ source. Animations are created from a set of codice_1 pictures; this technique was commonly used in the time that "Warcraft" and other RTS had come out.
"Stratagus" and "Wargus" have been ported to run on Pocket PC, Symbian and Android devices. Wargus has also been ported to the GP2X and Open Pandora Linux handhelds.
Reception.
"Stratagus" was downloaded alone from Sourceforge.net between 2004 and June 2017 over 185,000 times.