A more recent version of Gyachi is here : https://launchpad.net/~loell/+archive/ppa

Has anyone managed to do voice calls with Gyachi ?

FYI, to do voice/video calls with Windows interlocutors, I recommend :
- Ekiga (which exists also on Windows)
- Empathy (with Telepathy PPA , and ubuntu-restricted-extras package, and of course a Jabber account e.g. gmail address), that can do voice&video calls with Windows Gtalk interlocutors
- Skype (which exists also on Windows), but this one is not open-source