Designing ELF modules

LWN:
'ELF modules give the kernel a controlled way to run user-space helper code, and they make it easy to develop and distribute that code with the kernel itself. That latter aspect, in particular, distinguishes ELF modules from the existing "usermode helper" mechanism, which depends on programs developed and shipped separately from the kernel.'

GKH via LWN:
"sees uses for these modules as a way to implement USB drivers in user space, perhaps bringing some existing user-space drivers into the kernel tree in the process."

Hmm, presumably then user-space drivers that implement features like USB drivers would have to be GPLv2? Shipping userspace drivers with the kernel could be a win if existing drivers must be code-reviewed with usual standards before acceptance, but not at the cost of massively merging permissively licensed code into the kernel. OTOH, IIRC, device-tree compiler is permissively licensed, and no one cried foul there.