There are 2 mailing lists for flamingo-mc. See the MailingLists for details.
User can contribute to this open source project by reporting bugs. For Flamingo 4 we use Git to manage bugs, issues and new features. If you found a bug or you like to see a feature implemented in Flamingo 4, please report it in http://github.com/flamingo-geocms/flamingo/issues.
If you want to get involved as a Developer then you could start with getting the project up and running by building Flamingo 4 from source. See the Buildfromsource page for details.