Hi all, I am new here. I used to design my MCU based projects by breadboarding with Arduino Mini Pro board and then making a custom PCB with the project specific IO and an atmega328p with bootloader that makes the board looks to the Arduino IDE identical to an Arduino Mini Pro.

I like to do the same with ARM processors and the teensy 3.1 looks very promising.

How open is the teensy 3.1's bootloader and how difficult it is (technically and legally) to make my custom board look to the IDE like a teensy 3.1? For the atmega328p I am using an Atmel avrisp mkII to burn the bootloader after assembling the board. What is the equivalent for teensy 3.1?

My projects are open source but I don't sell them so I want to make it easy for people that want to build them.