Asked Mike Hu at Onyx International for the drivers. Waiting for a reply.
Edit: The email message failed to deliver. Maybe the address is no longer valid.
Koudijs, could you take a look at this page:
https://github.com/onyx-intl/booxsdk. It says the directory imx31 contains the complete "toolchain" for the M90. Does it mean it contains the drivers?
Looks like
http://opensource.onyx-international.com/ has been updated today with the zip file
boox-opensource-20120205.zip