Marlin is a FW for 3D printing. I've bent it to use with my cheese making equipment. This may seem slightly outside of Marlin's purpose but I didn't want to remake a PID/Temp/Stepper controller or web interface.
See README-Compiling.md for instructions on setting up Arduino IDE.
Marlin is published under the GPL license because we believe in open development. The GPL comes with both rights and obligations. Whether you use Marlin firmware as the driver for your open or closed-source product, you must keep Marlin open, and you must provide your compatible Marlin source code to end users upon request. The most straightforward way to comply with the Marlin license is to make a fork of Marlin on Github, perform your modifications, and direct users to your modified fork.
While we can't prevent the use of this code in products (3D printers, CNC, etc.) that are closed source or crippled by a patent, we would prefer that you choose another firmware or, better yet, make your own.