Developers are welcome to contribute to Quokka. If you are developing a new plugin for Quokka, you are encouraged to license it under an Apache License 2.0 and develop it under the Quokka source tree.
Quokka was deliberately split into core and contrib modules. All extensions including plugins, dependency sets and XML catalogues are under the contrib module here. Commit access to the contrib module will be granted to anyone who has developed a plugin. The core module on the other hand will probably be a little more tightly controlled.