Lukas,
The proper legal contact would be Mark Patrick (Mark.Patrick@nxp.com) in our "IP Counseling and Global IP Defensive Matters" team. Mark will probably contact me as the technical expert on the library, and I'll tell him what I told you: I'm unaware of any patent issues that would prevent our customers from using this software.
If you haven't already, you should read the software license contained in the NXP Sensor Fusion User Guide for terms and conditions.
Regards,
Mike