Discourse, Loomio and GitLab

[Benson Muite]

Am curious if any people have experience and suggestions for running 
Discourse ( https://github.com/discourse ), Loomio ( 
https://github.com/loomio ) and GitLab ( https://about.gitlab.com/ ). 
Discourse and Loomio can replace/augment mailing lists. These all use 
Ruby, and Fedora is using Discourse and expecting to use GitLab.