LaTeX Project Public License
Encyclopedia
The LaTeX Project Public License (LPPL) is a software license originally written for the LaTeX
system. Software distributed under the terms of the LPPL can be regarded as free software
, however it is not copyleft
ed.
Besides the LaTeX base system, the LPPL is also used for most third-party LaTeX packages. Software projects other than LaTeX rarely use it.
's original license for TeX, which states that the source code for TeX may be used for any purpose but a system built with it can only be called 'TeX' if it strictly conforms to his canonical program. The incentive for this proviso was to ensure that documents written for TeX will be readable for the foreseeable future – and indeed, TeX and its extensions will still compile documents written from the early 1980s to produce output exactly as intended. Quoting Frank Mittelbach, the main author of the license: "LPPL attempts to preserve the fact that something like LaTeX is a language
which is used for communication, that is if you write a LaTeX document you
expect to be able to send it to me and to work at my end like it does at
yours".
The most unusual part of the LPPL — and equally the most controversial — used to be the 'filename clause': You must not distribute the modified file with the filename of the original file. This feature made some people deny that the LPPL is a free software license. In particular the Debian
Linux community considered excluding LaTeX from its core distribution because of this.
However, version 1.3 of the LPPL has weakened this restriction. Now it is only necessary that modified components identify themselves "clearly and unambiguously" as modified versions, both in the source and also when called in some sort of interactive mode. A name change of the work is still recommended, however. This appeased the Debian community.
In order to provide project continuity in the case that the copyright holder no longer wishes to maintain the work, maintenance can be passed on to another (or from maintainer to maintainer). This can either be declared by the copyright holder or, in the event that the copyright holder is no longer able to be contacted, by the individual taking over maintenance, with a three month gap after their public intention to take over the maintenance. The modifying clause discussed above does not hold for the current maintainer of the work.
project holds the copyright for the text of the LPPL, but it does not necessarily hold the copyright for a work released under the LPPL. The author of the work holds copyright for the work, and is responsible for enforcing any violations of the license (or not).
Unlike the works released under the LPPL, the LPPL itself is not freely modifiable. While copying and distribution is allowed, changing the text of the LPPL is not. However, it may be used as a model for other licenses provided they do not reference the LPPL.
LaTeX
LaTeX is a document markup language and document preparation system for the TeX typesetting program. Within the typesetting system, its name is styled as . The term LaTeX refers only to the language in which documents are written, not to the editor used to write those documents. In order to...
system. Software distributed under the terms of the LPPL can be regarded as free software
Free software
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
, however it is not copyleft
Copyleft
Copyleft is a play on the word copyright to describe the practice of using copyright law to offer the right to distribute copies and modified versions of a work and requiring that the same rights be preserved in modified versions of the work...
ed.
Besides the LaTeX base system, the LPPL is also used for most third-party LaTeX packages. Software projects other than LaTeX rarely use it.
Unique features of the license
The LPPL grew from Donald KnuthDonald Knuth
Donald Ervin Knuth is a computer scientist and Professor Emeritus at Stanford University.He is the author of the seminal multi-volume work The Art of Computer Programming. Knuth has been called the "father" of the analysis of algorithms...
's original license for TeX, which states that the source code for TeX may be used for any purpose but a system built with it can only be called 'TeX' if it strictly conforms to his canonical program. The incentive for this proviso was to ensure that documents written for TeX will be readable for the foreseeable future – and indeed, TeX and its extensions will still compile documents written from the early 1980s to produce output exactly as intended. Quoting Frank Mittelbach, the main author of the license: "LPPL attempts to preserve the fact that something like LaTeX is a language
which is used for communication, that is if you write a LaTeX document you
expect to be able to send it to me and to work at my end like it does at
yours".
The most unusual part of the LPPL — and equally the most controversial — used to be the 'filename clause': You must not distribute the modified file with the filename of the original file. This feature made some people deny that the LPPL is a free software license. In particular the Debian
Debian
Debian is a computer operating system composed of software packages released as free and open source software primarily under the GNU General Public License along with other free software licenses. Debian GNU/Linux, which includes the GNU OS tools and Linux kernel, is a popular and influential...
Linux community considered excluding LaTeX from its core distribution because of this.
However, version 1.3 of the LPPL has weakened this restriction. Now it is only necessary that modified components identify themselves "clearly and unambiguously" as modified versions, both in the source and also when called in some sort of interactive mode. A name change of the work is still recommended, however. This appeased the Debian community.
In order to provide project continuity in the case that the copyright holder no longer wishes to maintain the work, maintenance can be passed on to another (or from maintainer to maintainer). This can either be declared by the copyright holder or, in the event that the copyright holder is no longer able to be contacted, by the individual taking over maintenance, with a three month gap after their public intention to take over the maintenance. The modifying clause discussed above does not hold for the current maintainer of the work.
Copyright holders
The LaTeXLaTeX
LaTeX is a document markup language and document preparation system for the TeX typesetting program. Within the typesetting system, its name is styled as . The term LaTeX refers only to the language in which documents are written, not to the editor used to write those documents. In order to...
project holds the copyright for the text of the LPPL, but it does not necessarily hold the copyright for a work released under the LPPL. The author of the work holds copyright for the work, and is responsible for enforcing any violations of the license (or not).
Unlike the works released under the LPPL, the LPPL itself is not freely modifiable. While copying and distribution is allowed, changing the text of the LPPL is not. However, it may be used as a model for other licenses provided they do not reference the LPPL.