MAME's main purpose is to be a reference to the inner workings of the emulated machines. This is done both for educational purposes and for preservation purposes, in order to prevent historical software from disappearing forever once the hardware it runs on stops working. Of course, in order to preserve the software and demonstrate that the emulated behavior matches the original, you must also be able to actually use the software. This is considered a nice side effect, and is not MAME's primary focus.
It is not our intention to infringe on any copyrights or patents on the original games. All of MAME's source code is either our own or freely available. To operate, the emulator requires images of the original ROMs, CDs, hard disks or other media from the machines, which must be provided by the user. No portions of the original game code are included in the executable.
MAME is free. Its source code is free. The project as whole is under distributed under the GNU General Public License, version 2 (GPL-2.0), but most of code (including core functionality) is available under the BSD-3-clause license.
ROM, CD, hard disk and other media images are all copyrighted material. They cannot be distributed without the explicit permission of the copyright holder(s). They are not "abandonware", nor has any of the software supported by MAME passed out of copyright.
MAME is not intended to be used as a tool for mass copyright infringement. Therefore, it is strongly against the authors' wishes to sell, advertise, or link to resources that provide illegal copies of ROM, CD, hard disk or other media images.
Because the name MAME is trademarked, you must abide by the rules set out for trademark usage if you wish to use "MAME" as part of the name your derivative work. In general, this means you must request permission, which requires that you follow the guidelines above.
The version number of any derivative work should reflect the version number of the MAME release from which it was was derived.
For questions regarding the MAME license, trademark, or other usage, go to http://mamedev.org/.
MAME is a registered trademark of Gregory Ember.