There are drivers for these chips to create a virtual COM port: your software talks to the newly appeared COM port, the driver translates this into USB-data and the chip translates this back to TTL-level RS232.
However, it is not as elegant, and the user can always select a different COM port in your software's settings -- one that might not be the right one. Wouldn't it be much cooler if you simply could plug in your USB-enabled device, the 'found new hardware'-dialog told you that it is a 'CreaCon Widget', no extra COM port, and the software automatically picks up on it?
This is possible with the D2XX direct drivers -- with a few simple API calls, you can send bytes to the chip (via USB, obviously) which then translates this into TTL-level RS232. Which means no more virtual COM ports, auto-detect of the device, and all sorts of neat tricks.
I found some good sample code, and I will develop this further for use in my MaxPWM kit, which will allow you to program the color cycles and/or command the module directly through USB.