Simlar – open-source, easy, encrypted, free phone calls (simlar.org)

Their server are based in Germany and license of their code is GPL licensed. Has anyone tried this app and/or were there any security expert auditing of the code?

ZRTP support is provided by liblinphone/mediastreamer2.

https://tools.ietf.org/html/rfc6189

https://www.linphone.org/technical-corner/liblinphone/overvi...

How does this compare to Signal[0]? Seems to be offering similar feature set, actually minus secured text messaging...

[0]: https://whispersystems.org/