Up to date contribution information can be found in CONTRIBUTING.md in the source code repository.
GitHub Repositories
You can use the code from these repositories to experiment, test, build, create patches, issue pull requests, etc.
https://github.com/eclipse-mosquitto/mosquitto.rsmb - Project repository hosted on GitHub.
https://github.com/eclipse-mosquitto/mosquitto - Project repository hosted on GitHub.
GitHub Organization
You can use the code from these repositories to experiment, test, build, create patches, issue pull requests, etc.
eclipse-mosquitto - Project repository hosted on GitHub.