The VESC software is free and open source, and can be found on github. This is the source code for the firmware that runs on the VESC hardware:
this is source code of VESC Tool, which is used to configure, control and monitor the VESC hardware from desktop and mobile platforms:
The software is released under the GNU General Public License version 3.0. Instructions on how to set up an development environment and build the software can be found in the pages below this page.