Originally Posted By: djb
Note: 'Copyright', not 'Copywright'. It's easy to remember: it is the right to make a copy.
The law is clear this topic. There is no restriction on modifying something that you own.
The court rulings are far less clear. And since you aren't going to be drug before congress, but into court, it's the court rulings that are a problem.
Most aftermarket ECU ROM chips (including EPROM etc) are pretty clearly a violation of the copyright. They take the original code and modify the original maps/tables, writing both components onto an EPROM that they sell you. Objectively the bulk of the value is in the original code, and their contribution is trivial. But since the modified ROM is pretty much usable only on the original ECU, this copyright violation is almost never pursued.
All modern ECUs use 'flash' memory, which is re-writable in place. Re-flashing those with an update is a legal gray area. Updated tables are a derivative work, but just the tables are probably not eligible for copyright protection. Modified code is more complicated, but since the process doesn't create a new copy (except incidentally, which is the legal standard) you could probably win the case with only moderate to mild bankruptcy.
The situation could be worse. Last year the U.S. Supreme Court unexpected ruled in favor of Kirtsaeng in Kirtsaeng v. Wiley. That confirmed that the First Sale doctrine. As part of oral arguments, the justices discussed the possibility that eventually cars could never be legally resold without the buyer explicitly paying for new software licenses. That would make reselling many goods economically impossible.
The Kirtsaeng case cost many millions of dollars. It left the defendant deeply in debt, even with major legal contributions from the EFF and other public interest groups. We own them all our thanks for pushing back the insanity.
The map is just calibration data, modifying it would be just like copying a new file on top of your existing hard drive, and therefore unlikely to be a copy right violation.
Now if someone sell a replacement chip, instead of writing on top of the existing one, that would probably be in a gray area that can draw lawsuit. The easiest way to get around it is to just ask people to send in the ECU / chip to be reprogrammed instead. Most code and data are separated enough (file based, memory address based, etc) that they can easily modify the map without touching the code at all (except checksum or encryption related values).
I can see a lot of complain if someone is modding a playstation or xbox to play pirated games, but I don't see any party would want to complain about a modded ECU as long as they can void the warranty for any liability or damage.