Please refer to the following confirmation from the AE team.
NXP Debian release is using LA_OPT_NXP_Software_License, customer can modify device tree, build image and pre-install to the Authorized System with an NXP product, that is free of charge. Customer can check the details in flexbuild/LICENSE_SDK.txt. 2.3 is applied for NXP Debian.
Customer should notice that NXP provides flexbuild script which will download packages and build Debian image. Customer must not violate the license terms of each individual software package if they need to modify the code. For example, any modifications to the kernel code must be made in compliance with the kernel's license, which is GPL-2.0.
Regarding the paid license of video decoding, AFAIK, the packages integrated into NXP Debian don't need to pay. I recommend to ask more details from the information source.