MarlinFirmware/Marlin
Marlin is a firmware for RepRap 3D printers optimized for both 8 and 32 bit microcontrollers. Marlin supports all common platforms. Many commercial 3D printers come with Marlin installed. Check with your vendor if you need source code for your specific machine.
License & maintenance
GPL-3.0 is a copyleft license: products that include or modify it may have to publish their code.
Last code push today.