Discourse
server plugin
A platform for community discussion. Free, open, simple.
Grist
server native
Grist is a modern relational spreadsheet. It combines the flexibility of a spreadsheet with the robustness of a database.
Keycloak
client both
Open Source Identity and Access Management For Modern Applications and Services
Stackspin
client native
A platform that offers self-managed, click-and-play provisioning of online applications for Civil Society Organisations (CSOs).
Synapse
server native
Matrix homeserver written in Python/Twisted.