the thing is that building a work alike chip - one that speaks the same protocols, has the same pinout, (but a different USBID/part number)is perfectly OK - price competition is good right?

The vendors would have to write their own drivers but compared with the cost of spinning a chip that shouldn't be a big deal, if they'd come out and sold their chips on the open market as a clone they'd probably get a lot of business.

Of course one of the weird things about ft232s is that they're non-standard USB devices (don't meet the ACM spec). If the cloners made ACM compatible chips they wouldn't need to write drivers since all OSs have them built in these days.

Disclaimer: I build and sell open source USB boards, including serial devices (ACM, not ft232 compatible)