Stanton Scs.3M
Link to the website: http://www.enterthesystem.com/system3/scs3m/
The latest official MIDI mappings and script files will be available here when they're available.
This is the Mixxx Wiki - 
Mixxx is a free and open-source DJ software.
Manual
Hardware Compatibility
Reporting Bugs
Getting Involved
Contribution Guidelines
Coding Guidelines
Using Git
Developer Guide
Creating Skins
Contributing Mappings
Mixxx Controls
MIDI Scripting
Components JS
HID Scripting