Nowadays browsers and content management systems all have the plugin/module/addon/theme systems for users to extend at their own will. Developers can also submit plugin to share the plugin with others. The most famous examples are Firefox Addon and Wordpress Plugin Directory.
I want to ask that if there is an open source web system specifically designed for this need - to host plugins? Not just one plugin, but all plugins for one software?
Ideally it should allow developers to upload the plugin, have a public version for each update, and client software can check if there are any plugin available through the directory's API.
As an example, a CMS can have one such directory to host/display theme files.
Also is there a better keyword to describe this kind of system?