The folks who maintain MAME (Multiple Arcade Machine Emulator) are aiming to make the project completely open source in order to expand both its pool of supporters and its utility to developers and historians.

This is notable because MAME is seen to be the premier emulator for arcade games, and the volunteers who maintain it have done laudable work to preserve artifacts of the game industry in a playable state.

MAME's source code has long been freely available, but it's never technically been open source. Instead it's been available under a modified BSD license that prohibits, among other things, commercial use of the code. 

MAME engineer Miodrag Milanovic says that license was put in place to deter "misuse of MAME in illegal ways," but it also kept museums that charged entry fees from using MAME in their exhibits or legal license owners from using MAME to rerelease old games.

"There was intention to do this for years," Milanovic tells Gamasutra. "Our aim is to help legal license owners in distribuiting their games based on MAME platform, and to make MAME become a learning tool for developers working on development boards."

He hopes it will help advance the understanding of classic game development, encourage classic game license holders to allow MAME to distribute their old games for free, and attract more developers into supporting the project, which is now fully integrated with its sister project MESS (Multi Emulator Super System).

"From now on there will be only one release executable that covers all arcades, computers and consoles," says Milanovic. "But we will stay under name 'MAME,' that is our trademark." 

For more details on the project and to keep tabs on its development, check out the MAME website.