Download of Jamulus 3.9 for Mac was on the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The common filename for the program's installer is jamulus-3.3.5-mac.zip. The actual developer of this free software for Mac is corrados.
The most popular version of the application is 3.3. 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. Jamulus for Mac lies within Audio & Video Tools, more precisely Music Production.
From the developer:
The Jamulus application enables musicians to perform real-time jam sessions over the Internet. There is a Jamulus server which collects the audio data from each Jamulus client, mixes the audio data and sends the mix back to each client. The Jamulus program requires an ASIO sound card driver to be available in the system.
You may want to check out more Mac applications, such as Resound, Radiologik DJ or SoundByte, which might be similar to Jamulus.