OPAR is an archive of packages that extend the OTRS software.
Using OTRS' smart packaging tool, OPM - OTRS package manager, extensions can be built by any developer, packaged and passed on to other users. Through packaging of own changes to the system, the system is then more audit proof. Additionally, the package system backs up all files changed, to make sure that an uninstall is successful.
You can install the OPM files via OTRS package manager. You can create your own repository and add this repository in SysConfig.