I would like to point out that the modern way to er.. "sidestep" the windows activation process on a UEFI system is to simply install a new bootloader. This is accomplished simply by writing a compiled EFI program to the EFI boot partition and setting it as your bootloader. It them lies to the kernel and makes it think it's running on an already-activated OEM system. Look up WindSLIC, I can't really give a link here for obvious reasons.
To note: this is a single binary that works on all x86_64 UEFI systems and can be written to the boot partition as any other file. Additionally, you can write a program to change boot order on UEFI bioses from within a running OS; example: efibootmgr. So while it is probably infeasible to infect the BIOS itself, it is somewhat trivial to infect the bootloader and do whatever you desire.
Infecting the bootloader has been a known technique for a while though (google "bootkits") - long before UEFI, actually. They are the whole reason behind Microsoft pushing for SecureBoot. This is not new, nor what badBIOS is supposedly about.
To note: this is a single binary that works on all x86_64 UEFI systems and can be written to the boot partition as any other file. Additionally, you can write a program to change boot order on UEFI bioses from within a running OS; example: efibootmgr. So while it is probably infeasible to infect the BIOS itself, it is somewhat trivial to infect the bootloader and do whatever you desire.