Delta 66 1.1 for Mac could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The actual developer of this free Mac application is M-Audio.
From the developer:
Unified installer for all Delta cards under OS X.
What's new in this version:
Unified installer for all Delta cards under OS X. Use OS X 10.1.5 or any flavor of Jaguar (10.2.x). If you updated from 10.1.5 to 10.2, you must re-install the drivers. * * * If you are running any pre-Jaguar flavor, you must update to 10.1.5 via Apple Software Update (it's free) * * * Select "Multichannel Delta" as your output device in Live, Logic, Reason, etc.
You may want to check out more software for Mac, such as Route 66, Delta Riddle or Delta Loop, which might be related to Delta 66.