GLEP:23

Status Update
Repoman has been updated to check for the LICENSE syntax. Portage now handles ACCEPT_LICENSE and license groups, with NON-MUST-HAVE-READ's role handled by @EULA. Marking as Final as of 1/16/2014.

Abstract
Currently, every ebuild in the main Gentoo repository is required to have a valid LICENSE entry. However, the syntax of this entry is not officially defined and the entry itself is only used when outputting package details.

Motivation
Many users wish to regulate the software they install with regards to licenses for various reasons. Some want a system free of any software that is not OSI-approved; others are simply curious as to what licenses they are implicitly accepting.

Furthermore, some software requires that a user interactively accept its license for its author's to consider it legally binding. This is currently implemented using.

Ebuild LICENSE Variable
Most ebuilds are for software which is released under a single license. In these cases, the current LICENSE variable can remain as is. For example:

LICENSE="single-license"

However, there are several ebuilds for software which is released under several licenses, of which the user must accept one, some or all. To complicate this, some ebuilds include optional components which fall under a different license.

To accommodate these cases, LICENSE syntax should accommodate all functionality offered by a DEPEND string. To keep things simple, this GLEP proposes that the syntax be identical. For example:

LICENSE="mandatory-license       || ( choosable-licence1 chooseable-license-2 )         useflag? ( optional-component-license )"

License names may contain [a-zA-Z0-9] (english alphanumeric characters), _ (underscore), - (hyphen),. (dot) and + (plus sign). They must not begin with a hyphen, a dot or a plus sign.

License Groups
Almost all users are willing to install any software that is FSF-approved. Other users are willing to install any software and implicitly accept its license. To this end, implementations will also need to handle grouping of licenses.

At a minimum, there needs to be the groups,  ,   and. licenses are those that don't require manual acceptance for to be considered legally binding. This is the current behaviour of portage.

These groups are defined in a new file  in the   subdirectory of the tree (or overlays). Details of handling groups defined in overlays is implementation dependent.

The format of this file is:

... 

Also any line starting with # is ignored and may be used for comments. Group names use the same syntax as normal license names. Also license groups may contain other groups. License groups may not contain negated elements, so a group:

mygroup foo -bar -bla

is illegal.

ACCEPT_LICENSE
This GLEP proposes that a user be able to explicitly accept or decline licenses by editing a new variable  in  .  Again, to keep things simple, the syntax should be similar to that of other incrementals. For example:

ACCEPT_LICENSE="-* accepted-license -declined-license"

As an extension,  must also support. This GLEP proposes that the license group be prepended by the special character " ". For example:

ACCEPT_LICENSE="-* @FSF-APPROVED"

License groups may be negated with the result that all elements of that group are also negated.

Portage will also offer a package.license facility to offer this functionality on a per-package base (analog to package.keywords), other implementations may implement such a facility differently or not at all.

Behaviour
Unaccepted licenses will be treated like any other masked package, that is the user interface of an implementation will display a message listing any license that has to be accepted before the package can be merged with a pointer to the exact license text.

Past versions of this document proposed to handle license-masked packages like blockers, but this would be inconsistent with other visibility filters as well as the current blocker system (as a blocker affects two packages) and be more complicated to implement.

Rationale
An implementation of this proposal should make it easy for users wishing to regulate their software without affecting those that don't.

Reference Implementation
Available in portage svn repository under main/branches/license-masking

Backwards Compatibility
There should be no change to the user experience without the user explicitly choosing to do so. This mandates that the configuration variable be named  as some users may already have it set due to ebuilds using  's implementation. It also mandates that the default  be set to   in the main gentoo repository as implementations are not required to provide an internal default.

Copyright
This work is licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/.