Jitsi offers several advanced communication features, including secure video calls using ZRTP, conferencing, chat, file transfer, and cross-platform remote desktop sharing. It is available under the LGPL license.
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Secure VoIP, GNU SIP Witch, and replacing Skype with free software
http://planet.gnu.org –
"For the last few years I had been working when time was available on what is called the GNU Telephony Secure Calling Initiative.This initiative was originally started specifically to make passive voice communication intercept a thing of the past using free software and public standards, and came out of ideas from and the work of the New York City civil liberties community and New York Fair Use in
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