The Zero Install Injector makes it easy for users to install software without
needing root privileges. It takes the URL of a program and runs it (downloading
it first if necessary). Any dependencies of the program are fetched in the same
way. The user controls which version of the program and its dependencies to
use.

Zero Install is a decentralised installation system (there is no central
repository; all packages are identified by URLs), loosly-coupled (if different
programs require different versions of a library then both versions are
installed in parallel, without conflicts), and has an emphasis on security (all
package descriptions are GPG-signed, and contain cryptographic hashes of the
contents of each version). Each version of each program is stored in its own
sub-directory within the Zero Install cache (nothing is installed to
directories outside of the cache, such as /usr/bin) and no code from the
package is run during install or uninstall. The system can automatically check
for updates when software is run.