How to change the usb name of Atmel 32u4?
The Arduino '32U4 bootloader, Caterina, can be found under hardware/arduino/bootloaders/caterina. It requires LUFA in order to build.

With the technical part aside, note that you are not allowed to use the USB IDs assigned to Arduino LLC with products you intend to distribute under another name. You will need to acquire your own vendor ID from the USB-IF if you want to do so.