BSD licenses in the context of Berkeley Software Distribution

WebM is an audiovisual media file format. It is primarily intended to offer a royalty-free alternative to use in the HTML video and the HTML audio elements. It has a sister project, WebP, for images. The development of the format is sponsored by Google, and the corresponding software is distributed under a BSD license.

The WebM container is based on a profile of Matroska. WebM initially supported VP8 video and Vorbis audio streams. In 2013, it was updated to accommodate VP9 video and Opus audio. It also supports the AV1 codec.

The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or copyleft licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first copyleft license available for general use. It was originally written by Richard Stallman, the founder of the Free Software Foundation (FSF), for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition. The licenses in the GPL series are all copyleft licenses, which means that any derivative work must be distributed under the same or equivalent license terms. The GPL states more obligations on redistribution than the GNU Lesser General Public License and differs significantly from widely used permissive software licenses such as BSD, MIT, and Apache.

Historically, the GPL license family has been one of the most popular software licenses in the free and open-source software (FOSS) domain. Prominent free software programs licensed under the GPL include the Linux operating system kernel and the GNU Compiler Collection (GCC). David A. Wheeler argues that the copyleft provided by the GPL was crucial to the success of Linux-based systems, giving the contributing programmers some assurance that their work would benefit the world and remain free, rather than being potentially exploited by software companies who would not be required to contribute to the community.

The Mozilla Public License (MPL) is a free and open-source weak copyleft license for most Mozilla Foundation software such as Firefox and Thunderbird. The MPL is developed and maintained by Mozilla, which seeks to balance the concerns of both open-source and proprietary developers. It is distinguished from others as a middle ground between the permissive software BSD-style licenses and the GNU General Public License. As such, it allows the integration of MPL-licensed code into proprietary codebases, as long as the MPL-licensed components remain accessible under the terms of the MPL.

MPL has been used by others, such as Adobe to license their Flex product line, and The Document Foundation to license LibreOffice 4.0 (also on LGPL 3+). Version 1.1 was adapted by several projects to form derivative licenses like Sun Microsystems' Common Development and Distribution License. It has undergone two revisions: the minor update 1.1, and a major update version 2.0 nearing the goals of greater simplicity and better compatibility with other licenses.

VP8 is an open and royalty-free video compression format released by On2 Technologies in 2008.

Initially released as a proprietary successor to On2's previous VP7 format, VP8 was released as an open and royalty-free format in May 2010 after Google acquired On2 Technologies. Google provided an irrevocable patent promise on its patents for implementing the VP8 format, and released a specification of the format under the Creative Commons Attribution 3.0 license. That same year, Google also released libvpx, the reference implementation of VP8, under the revised BSD license.

A permissive software license, sometimes also called BSD-like or BSD-style license, is a free-software license which instead of copyleft protections, carries only minimal restrictions on how the software can be used, modified, and redistributed, usually including a warranty disclaimer. Examples include the GNU All-permissive License, MIT License, BSD licenses, Apple Public Source License and Apache license. As of 2016, the most popular free-software license is the permissive MIT license.