The 5.5.10 version of zoiper 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. This free Mac app was originally created by Zoiper.com. The application lies within Communication Tools, more precisely Texting & Video calls. Please check the Mac app with an antivirus before launch as it is downloaded from the developer's website, and we cannot ensure that it is safe.
From the developer:
ZoIPer (formerly known as Idefisk) is a SIP and IAX/IAX2 software phone, compatible with the Asterisk/CallWeaver platform and adaptive to any IP telephony system. It offers a great variety of features to cover all aspects that VoIP provides. Its great simplicity with enhanced interface brings a smooth and satisfying communications experience.
You may want to check out more Mac applications, such as Zoiper Softphone or Zoiper Click2Dial, which might be related to zoiper.