The 1.05 version of teensy for Mac is provided as a free download on our software library. This free software for Mac OS X was originally created by PJRC. Our antivirus analysis shows that this Mac download is malware free. The following version: 1.0 is the most frequently downloaded one by the program users. This free program was developed to work on Mac OS X 10.5.0 or later. The file size of the latest installer available for download is 4.8 MB.
From the developer:
The Teensy Loader program communicates with your Teensy board when the HalfKay bootloader is running, so you can download new programs and run them.
Teensy Loader always reads the latest version of your HEX file, so you can just compile your code, then press the pushbutton to program and run your code.
You may want to check out more Mac applications, such as WaxBee or teensyduino, which might be similar to teensy.