The 1.0 version of Sippy for Mac was available to download on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The actual developer of this free software for Mac is TerminalWorks. Sippy for Mac lies within Communication Tools, more precisely Texting & Video calls. We recommend checking the downloaded files with any free antivirus.
From the developer:
Sippy lets you make quick calls to your colleagues and friends either over the Internet or your local network. Therefore, you can replace your desk phone with Sippy desktop application and make Sippy your phone companion. Sippy is easy to configure and easy to use thanks to the super user-friendly interface designed for all your telephony needs.
You may want to check out more software for Mac, such as iChatOnLogin, MySpaceIM or TextMagic Messenger, which might be related to Sippy.