No, there is no version of JetShell that you can run on a Mac OS X operating system. All the available downloads are listed for Windows only.
You can find the downloads on the official website: http://www.jetaudio.com/download/iaudio_cw_jsfw.html
Unfortunately, no alternative is provided since these devices are configured to work only with certain software. However, to transfer data from your iAudio MP3, switch the device to MTP mode. This modifies the connection parameters for Windows to see it as a Plug-n-play device making it easier to transfer files from PC to device through My Computer/Computer. Therefore, go to Settings > Connectivity/Connection Mode and switch it to MTP.