I haven't seen anyone mention RetroShare.
From their website: "Retroshare creates encrypted connections to your friends. Nobody can spy on you. Retroshare is completely decentralized. This means there are no central servers. It is entirely Open-Source and free. There are no costs, no ads and no Terms of Service."
-Voice & Video
And other minor things.
BEST PART: You can hide your ip by running it through both Tor and I2P. (I2P being my fav)
How does it work?
Retroshare is a network of computers. These computers we call nodes and every user has it's own node. The exact location (the IP-address) of nodes is only known to neighbors. You invite someone to become a neighbor by sending your public key to them.
Forums use pseudonymous nicknames to identify people. The nickname system uses cryptographical keys to verify messages come from specific authors. The nickname information travels wherever the forum post goes.
If you send a message to a user, the system delivers it to his node by searching for a route by forwarding it via a chain of neighboring nodes. If you want a certain file, your node asks your neigbours and they in turn request it from their neighbors.
Extra technical stuff:
Network topology: decentralized Friend to Friend network (F2F)
Transport: IPv4 TCP+UDP, Tor
UPnP / NAT-PMP port forwarding support
Distributed hash table to locate friends
Optionally can use dynamic DNS
Connect to friends behind NAT with UDP
Transport encryption with TLS (OpenSSL)
Authentication with PGP keys
Services: chat, VoIP with video, multi-user chat, file search/file sharing, forums, link sharing, Retroshare mail
Extensible through plugins
As a baseline of what type of software you should use, Peer to Peer, Encrypted, Open Source, and doesn't require bullsoykaf like phone number or email. Feel free to add other requirements.
There have been other anons in this thread which explained the problems of having a central server: "kill 1 server to stop 100 people verses having to get each one by one" (more or less).
Closed source is a VERY obvious issue, no software should be recommended if it is closed source. Although I have seen several in OP's post.
If you want to talk about security and other fun stuff, you can add me on RetroShare or Tox, both are great software.https://privatebin.net/?9cac8a523e6515bc#EAcWwQbS4AKLVqyKVCs6LUEejSk9Kg+L+q5PGDNnUMs=