The contributors disclaim warranty and liability, but allow auxiliary distributors to offer such things on their own behalf.

Covered source code files must remain under the MPL, and distributors "may not attempt to alter or restrict recipients' rights" to it.

An executable consisting solely of MPL-covered files may be sublicensed, but the licensee must ensure access to or provide all the source code within it.

[4] The initial author of MPL code may choose to opt out of this GPL compatibility by adding a notice to its source files.

Version 1.0 of the MPL was written by Mitchell Baker in 1998 while working as a lawyer at Netscape Communications Corporation.

[23] Less than a year later, Baker and the Mozilla Organization would make some changes to the MPL, resulting in version 1.1, a minor update.

[6] For these reasons, earlier versions of Firefox were released under multiple licenses: the MPL 1.1, GPL 2.0, and LGPL 2.1.

[18][27] The revision team was overseen by Baker and led by Luis Villa with key support from Gervase Markham and Harvey Anderson.