What are some alternatives?
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Squiggle - Squiggle is a free server-less peer to peer LAN messenger.
MyChat - Secure instant messenger for any network
LAN Messenger - LAN Messenger is a decentralized UDP IM-style chat client which supports usernames...
MagicPad - Free, simple, and private, offline text encryption suite.
Feem - Share files offline. No servers. No cloud. No limits.