Softros LAN messenger - LAN messenger for an internal office chat for home or business users. It does not require a server and is very easy to install and use. It supports personal chats, group chats, message brodcasting, files transfer and remote desktop access.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
MyChat - Secure instant messenger for any network
Drift - A messaging app that helps you grow your business.
BORGChat - BORGChat is a LAN messaging software program.
Slack for Mac - A new, improved Slack desktop app for Mac