Mattermost
Mattermost is an open-source, self-hostable online chat service with file sharing, search, and integrations. Designed as an alternative to Slack, it was founded by a Canadian-led team and is widely used by enterprises and governments for secure communications.
Pidgin
Pidgin is a free and open-source multi-protocol instant messaging client. Canadian open-source developers have long been contributors to Pidgin and its underlying libpurple library, which supports dozens of chat protocols.