hairless-midiserial 0.4 for Mac was available to download from 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 Mac application is Angus Gratton. We recommend checking the downloaded files with any free antivirus.
From the developer:
Hairless MIDISerial Bridge is an easy way to connect serial devices (like Arduinos) to send and receive MIDI signals. It has no dependencies and can be run out of the box on nearly any computer. It improves FTDI latency - this means better MIDI latency when using FTDI-based devices, like the Arduino Duemilanove.