The technical committe was asked in #681419 by the policy maintainers
to determine as a matter of technical whether alternative dependencies
on non-free packages were acceptable in main.
==== RESOLUTION ====
Whereas:
1. The Debian Policy Manual states (§2.2.1) that packages in main
"must not require or recommend a package outside of main for
compilation or execution". Both "Depends: package-in-non-free" and
"Recommends: package-in-non-free" clearly violate this requirement.
The Technical Committee has been asked to determine whether a
dependency of the form "package-in-main | package-in-non-free"
complies with this policy requirement, or whether virtual packages
must instead be used to avoid mentioning the non-free alternative.
2. Both options have the following effects in common, meeting the
standard that main should be functional and useful while being
self-contained:
(a) Package managers configured to consider only main will install
package-in-main.
(b) Package managers configured to consider both main and non-free
will prefer to install package-in-main, but may install
package-in-non-free instead if so instructed, or if
package-in-main is uninstallable.
(c) If package-in-non-free is already installed, package managers
will proceed without installing package-in-main.
3. The significant difference between these two options is that the
former makes the non-free alternative visible to everyone who
examines the dependency relationship, while the latter does not.
4. Merely mentioning that a non-free alternative exists does not
constitute a recommendation of that alternative. For example, many
free software packages state quite reasonably that they can be
compiled and executed on non-free platforms.
5. Furthermore, virtual packages are often a clumsy way to express
these kinds of alternatives. If a package happens to require any
of several implementations of a facility that have a certain
option, then it can either depend on suitable alternatives
directly, or its maintainer can first attempt to have fine-grained
virtual packages added to each of the packages they wish to permit.
In some cases this may be appropriate, but it can easily turn into
quite a heavyweight approach.
Therefore:
6. The Technical Committee resolves that alternative dependencies of
the form "Depends: package-in-main | package-in-non-free" are
permissible in main, and do not constitute a violation of the
policy clause cited in point 1.
7. We nevertheless recommend that packages in main consider carefully
whether this might cause the inadvertent installation of non-free
packages due to conflicts, especially those with usage
restrictions.
==== END OF RESOLUTION ====
The committee would like to thank everyone who participated in the
discussion of #681419.
Please see http://bugs.debian.org/681419 for discussion of
this bug.
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