From Community Help > Repositories, Software in Ubuntu’s repository is divided into four categories or components: main, restricted, universe and multiverse.
- Main: The main component contains applications that are free software, can be freely redistributed and are fully supported by the Ubuntu team.
- Universe: The universe component is a snapshot of the free, open-source, and Linux world. It houses almost every piece of open-source software, all built from a range of public sources.
- Restricted: Proprietary drivers that make it possible to install Ubuntu and its free applications on everyday hardware
- Multiverse: The multiverse component contains software that is not free, which means the licensing requirements of this software do not meet the Ubuntu main component licence policy.
We can understand why restricted components are provided. As the page says,
Our commitment is to only promote free software – or software
available under a free licence. However, we make exceptions for a
small set of tools and drivers that make it possible to install Ubuntu
and its free applications on everyday hardware. These proprietary
drivers are kept in the restricted component. Please note that it may
not be possible to provide complete support for this software because
we are unable to fix the software ourselves – we can only forward
problem reports to the actual authors. Some software from restricted
will be installed on Ubuntu CDs but is clearly separated to ensure
that it is easy to remove. We will only use non-open-source software
when there is no other way to install Ubuntu. The Ubuntu team works
with vendors to accelerate the open-sourcing of their software to
ensure that as much software as possible is available under a free
licence.
However, why is the multiverse category included? What is the purpose of it?
There is wide range of non-free/proprietary applications & software included in the multiverse category. I don’t understand why this is considered a good thing.
Best Answer
The distinction between restricted and multiverse is that Ubuntu itself pledges to support the software in restricted, whereas software in multiverse is provided by Ubuntu but with no guarantee of Ubuntu support. I's not really fair to say universe and multiverse software is "unsupported", just that support will be dependent on the third party that produced it, or other third parties, and/or the "Ubuntu community": volunteers that package software for Ubuntu. This is opposed to software in main and restricted where Ubuntu have allocated dedicated people to ensure its support.
The distinction between restricted/multiverse and main/universe is that the software in restricted/multiverse is not fully free by Ubuntu's definition of free software, though it is still free enough for Ubuntu to distribute it in a repository. Usually this means that it contains binary code for which the source is not available, though sometimes it can be other licensing issues.
So, technically, multiverse contains software that:
What are examples of packages in multiverse?
Chiefly, ubuntu-restricted-extras is a metapackage containing a suite of software Ubuntu thinks you really are likely to want, even though it's not open source software.
Installer for Adobe's Flash plug-in
Microsoft Core Fonts for the Web
A selection of video or audio codecs with non-free licenses
Unrar
Other packages in multiverse, but not part of ubuntu-restricted-extras, include a small range of Linux based software included either because Ubuntu thinks you're very likely to want to install it on Ubuntu, or because it is very much open source software in spirit but misses out on qualifying with Ubuntu's definition of free software for some reason, such as by including some binary code without source, or some license terms that make its license incompatible (eg a non-commercial clause, or any other "custom" clauses added to otherwise compatible open source licenses).