I'm pretty sure DMCA or friends WON'T let you, legally, make a chip that pretends to be another chip
The DMCA doesn't cover this issue. The closest it comes is explicitly protecting reverse engineering for the purposes of interoperability. Creating a chip that works just like the FTDI chip is not illegal. Putting FTDI's marks on the top of your chip is a violation of trademark law. Distributing FTDI's driver would be a violation of copyright law. Downloading FTDI's driver without permission is also a violation of copyright law, so who distributes/downloads the driver affects who violates copyright there. Finally, using the driver without permission is also a violation of copyright law. AFAIK there is no legal precedent (and certainly no applicable laws) which cover the use of someone else's USB ID, unless you are doing it with the intent to cause some kind of harm, or cause harm through negligence.
Any possible claims over these clone chips center around driver copyright or misuse of trademarks. Or, of course, patent abuse, but that seems relatively unlikely here. FTDI is in extremely well-traveled territory.
So some company makes a fake Ford, which has acceleration problems. It crashes, kills someone, and Ford is to blame because it had a Ford badge? ...
If you take your fake Ford in for service, they detect that it's a fake, and instead of telling you that it's fake (and possibly removing your emblems) they reflash your PCM, deliberately causing your car not to start, how will you feel about that? Will you solely blame the manufacturer of your fake car, or will you be angry at the dealership for disabling your car?