This project contains 3D printable capacitive buttons, and the Teensy code to drive them. Buttons print flat and then 'pop through'.
SMidi is open source hardware. This github repository hosts the OpenSCAD source, the Arduino source, and possibly the rendered STL images for quick access.
Hardware designs (schematics and CAD) files are licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License and follow the terms of the OSHW (Open-source hardware) Statement of Principles 1.0.