You've been able to make your own custom Steam Controller profiles for a while. It's now time to create your own Steam Controller.
Valve has released the computer-aided design (CAD) files for the Steam Controller to the public.
In a post on Steam, the company made available a .zip file that would allow anyone with the technical know-how to create their own version of the Steam Controller, or design accessories for it.
The files include the geometry of all "externally visible parts", and Valve is encouraging users to 3D print and share their designs with the community.
As for commercial use, Valve will need to first approve designs and give permission, before users are allowed to sell their work.