The
Mozilla Public License (MPL) is a
free and
open source software license. Version 1.0 was developed by
Mitchell Baker when she worked as a
lawyer at
Netscape Communications Corporation and version 1.1 at the
Mozilla Foundation. The MPL is characterized as a hybridization of the
modified BSD license and
GNU General Public License.
The MPL is the license for the
Mozilla Application Suite,
Mozilla Firefox,
Mozilla Thunderbird and other Mozilla software. The MPL has been adapted by others as a license for their software, most notably
Sun Microsystems, as the
Common Development and Distribution License for
OpenSolaris, the open source version of the Solaris 10 operating system, and by
Adobe, as the license for its
Flex product line.
Terms
The license is regarded as a weak
copyleft. Specifically,
source code copied or changed under the MPL must stay under the MPL.
The MPL was approved both as an
Open Source software license by the
Open Source Initiative and as a
Free Software license by the
Free Software Foundation.
Compatibility with other licenses
Unlike strong copyleft licenses, the code under the MPL may be combined with
proprietary files in one program ("Larger Work"). For example,
Netscape 6 and later releases were proprietary versions of the Mozilla Application Suite, by adding the proprietary AIM and other parts. The MPL treats the source code file as the boundary between MPL code and proprietary parts, meaning that a certain source file (e.g., C++, JavaScript or XUL file) is either fully MPL or fully proprietary. The
GPL, in contrast, uses the process boundary of the executable as the license boundary (for details, see
GPL).
Compatibility with GPL
The
Free Software Foundation (FSF) considers the license a
free software license, albeit one with a weak copyleft. However, "unlike the
X11 license" the license has "some complex restrictions" making it
incompatible with the
GNU GPL. They urge people not to use the license because of this incompatibility unless the provision in section 13 of the MPL is exercised to provide the work under either the GPL or any other GPL-compatible license.
For these reasons, the Mozilla Suite and Firefox have been relicensed under
multiple licenses, including the MPL,
GPL and
LGPL.
MPL-based licenses
