>> The driver is copyrighted and trademarked and abusing the not illegal to abuse PID/VID system to trick a driver
Yeah, the compatible and clone counterfeit chip maker are bad boys for letting you, the windows user in a gray area when using the official FTDI driver.
It's not nice, but not illegal. It's the point of a compatible to be compatible.
The EULA is not agreed by most people using recent windows, there is no EULA on th FOSS driver, so most people did not agree to respect anything in the EULA.
Microsoft has that covered for their online services, (If you have windows you agreed to the EULA, and same for all the online services like windows update) Don't like the terms and they suggest returning the software or disabling/not using services which you do not want. FTDI's driver license is very explicit about how mad they will get if you use fake chips with their software. (Microsoft is a lot more livid though about how bad counterfeit Microsoft windows and the ways they can make it go wrong for you the user, might break the OS, no updates, things might not work if we feel like it, ...)
"7.4. How is the software updated? We may automatically check your version of the software. We may also automatically download updates to the software from time to time. You agree to accept such updates subject to these terms unless other terms accompany the updates.
If so, those other terms apply. Microsoft isn't obligated to make any updates available and doesn't guarantee that we'll support the version of the system for which you licensed the software. Such updates may not be compatible with software or services provided by third parties."
A transitive ToS. I'm surprised microsoft has just one general ToS for "Microsoft Services" (The built in EULA is similar although it has pages and pages of what happens if you are detected as a fake windows copy and all the ways Microsoft will be mad at you and what will break and how Microsoft can mangle your OS to "repair" the counterfeiting) For Microsoft their view is you don't like our terms don't use the service basically. Actually they do seem to have supplemental ones and all manner of them scattered about.
(They also say nothing about loss of use or damage should windows genuine advantage (such a happy name for a DRM system that also calls home) get angry at you even if you didn't originally install windows)(For a time Microsoft did bad things to fake copies but now they are less forceful and its more a nag to death type system than dead system type of thing, Vista really sucked on that front and it functionally acted as a timebomb type program, SP1 "fixed" that to the normal nagging)
A third party written driver has no obligation to use FTDI's anti-counter fitting measures and would be perfectly legal as a piece of software and could be called fully compatible with PID0000 fake and real FTDI parts but just directly cloning FTDI's software is not legal. As others have said PID/VID collisions themselves are not illegal so the driver can even advertise such PID/VID combos to FTDI's chagrin just nothing in the driver can refer to FTDI just call it the "very compatible very drunk virtual serial port driver". Write your own config tools (probably not very complicated) and you can be FTDI trademark/copyright free.