If you have evidence of their intent then it would be interesting to see that.
There's evidence presented in this thread, by people familiar with reimplementing their interface. I see you didn't bother to read the thread.
I didn't suggest that what they were doing was not illegal, just that I support it. It wouldn't be the only thing considered illegal that I support.
But in this case you're celebrating denial of service to a user who may have acted in good faith. That's a shitty thing to be happy about. Why do you like taking advantage of people?
They're good enough that their drivers are apparently able to support a wide range of hardware that they didn't build. I'd say that's doing a pretty decent job.
Only due to ignorance. The decent job was done by the people who make clone chips who implemented their interface. If they had written the driver to support disparate chips, that would have been a significant accomplishment. Writing a driver for their chip was not. In addition, software is expecting to see that driver.
What exactly are they bad at doing?
Ironically, writing drivers, and packaging them for versions of Windows with driver signing. It was literally years after the release of Windows 7 before they had a decent package of Windows 7 drivers that would reliably work with their hardware. But because applications expect to see their driver, the only option would be to write a driver which supported their driver interface. Microsoft proved in the past that chasing a software interface is a fool's game, because it can be updated periodically solely for the purpose of decreasing interoperability.
other companies want to leech off them and get support
Nobody is expecting anyone to contact FTDI for support, but now that they've done this to their driver, they will be contacted. So in fact, if their goal was to avoid support contacts, this was a staggeringly stupid move.
Necessary for meaningful interoperability.
from them without paying anything for it.
FTDI became a de facto standard, and they are reaping the results now. They are using copyright (AFAICT, no patents are involved, this is deeply old technology) as a bludgeon in a way that will harm users and achieve none of your stated goals. As the only thing they will accomplish is harm to users and the generation of ill will, the fact that you are pleased by these actions is unsurprising, at least to me. You seem to revel in such abuse.