Description:

Zero Install is a decentralized cross-distribution software
installation system available under the LGPL. It allows software
developers to publish programs directly from their own web-sites,
while supporting features familiar from centralized distribution
repositories such as shared libraries, automatic updates and digital
signatures. It is intended to complement, rather than replace, the
operating system's package management. 0install packages never
interfere with those provided by the distribution.

0install does not define a new packaging format; unmodified tarballs
or zip archives can be used. Instead, it defines an XML metadata
format to describe these packages and the dependencies between them. A
single metadata file can be used on multiple platforms (e.g. Ubuntu,
Debian, Fedora, openSUSE, Mac OS X and Windows), assuming binary or
source archives are available that work on those systems.

0install also has some interesting features not often found in
traditional package managers. For example, while it will share
libraries whenever possible, it can always install multiple versions
of a package in parallel when there are conflicting
requirements. Installation is always side-effect-free (each package is
unpacked to its own directory and will not touch shared directories
such as /usr/bin), making it ideal for use with sandboxing
technologies and virtualization.

The XML file describing the program's requirements can also be
included in a source-code repository, allowing full dependency
handling for unreleased developer versions. For example, a user can
clone a Git repository and build and test the program, automatically
downloading newer versions of libraries where necessary, without
interfering with the versions of those libraries installed by their
distribution, which continue to be used for other software.