First, only signed drivers should be accepted:
What Microsoft markets in its documentation as a security gain and as an indispensable feature for Digital Rights Management (DRM) has a bitter aftertaste: So far, only those who equip themselves with corresponding certificates from Verisign and pay around 500 US dollars per year for this can create such a signature.
But from signed drivers (with which open-source drivers will already have a real problem) to signed applications is not far. And for open source projects, it is usually not so easy to get the money for certificates.