The MAME project as a whole is distributed under the terms of the GNU General Public License, 2 (GPL-2.0), since it contains code made available under multiple GPL-compatible licenses. Over time, MAME absorbed the sister-project MESS (Multi Emulator Super System), so MAME now documents a wide variety of (mostly vintage) computers, video game consoles and calculators, in addition to the arcade video games that were its initial focus. The fact that the software is usable serves primarily to validate the accuracy of the documentation (how else can you prove that you have recreated the hardware faithfully?). The source code to MAME serves as this documentation. This is achieved by documenting the hardware and how it functions. As electronic technology continues to rush forward, MAME prevents this important 'vintage' software from being lost and forgotten. MAME's purpose is to preserve decades of software history. MAME originally stood for Multiple Arcade Machine Emulator.