I'm the lead developer of https://github.com/uTox/uTox We're exclusively str8c. And will trade deeper knowledge of safe str8c, (as it pertains to a crypto/security project) for code donations. I.e., we'll teach you to write better/safer C if you wanna help us close some issues. :D
µTox. https://github.com/uTox/uTox
Configure it so it uses the tor network as a proxy (from settings: "Proxy (SOCKS 5) localhost:9050"). Make sure to have tor installed (apt-get install tor). Check the "Force uTox to always use proxy" from the options.
Cheers.