The 1.15 version of KX3UI 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. KX3UI for Mac lies within System Tools, more precisely Device Assistants. We recommend checking the downloaded files with any free antivirus. The actual developer of this software for Mac is Pignology, LLC.
From the developer:
KX3UI provides a graphical interface for controlling the Elecraft radios from your Mac. You can connect with a wired serial port or using the Piglet wireless serial adapter. The app has a CW/DATA terminal that uses the radio's built-in CW/DATA decode functionality.
You may want to check out more Mac applications, such as Portable Nvu, SpaceReporter or Matchprint Virtual, which might be related to KX3UI.