A quick google search found this info on the Arduino Forum which a user kindly shows the rules relating to this stuff.
The Optiboot bootloader is not actually an Arduino 'product'. Boards you design and software you write using Arduino IDE and libraries does not need to be disclosed to anybody, other than having the objects available (probably in a hidden part of your product's support website, in a "firmware" sub section) for some reason relating to being able to build the source against newer versions of Arduino.
I am currently making a product which I intend to use Arduino libraries and IDE and bootloader for fast development, but the board, schematics, and essentially the application code except for the libraries from Arduino will be mine. If you copy or build stuff specifically for/from Arduino hardware, you must(?) release certain source/schematics etc.