You could have downloaded teensyduino 1.18 for Mac from our application library for free. The application lies within Productivity Tools, more precisely Office Tools. Teensyduino works fine with Mac OS X 10.5.0 or later. The most popular version among teensyduino for Mac users is 1.1. The actual developer of this free software for Mac is PJRC.
From the developer:
Teensyduino is a software add-on for the Arduino, which helps run sketches on the Teensy and Teensy . All communication is performed at full native 12 Mbit/sec USB speed. Serial includes built-in flow control, so the effective speed will be as fast as your code can read.
You may want to check out more Mac applications, such as pdf-DocPro, Instant PDF or Padre, which might be related to teensyduino.