If I understood correctly, you only need proprietary parts for the
kernel that runs *in* the card. The kernel running on your actual system
does not need proprietary parts, leaving you free to use a different kernel.
The binary provision for drivers is a bit vague at best When some parts of the kernel becomes gpl3, which it might, distributing binary drivers for the kernel will no longer be allowed.
Sigma Designs work around this by having their binary parts running as user space programs.