Failed English comprehension
@AC That letter does not say that. You are making unwarranted assumptions. The modified/derived code would still count as OSS (depending on licence, but you're assuming GPL, so let's go with that). The letter says that the OSS code is included so you can assume the modified code is included. What is not included is the rest of the source code for the car that is not OSS and has not been tainted with GPL linking etc. This is legal and complies with GPL v2. If any GPL v3 code is included that is a different matter, but there is no reason to assume that there is.