Thanks for the output.
In the first mode, the device is in ActiveStink mode, requiring an RNDIS driver *and* the synching application behind it. The RNDIS driver is a bit more complicated than a standard Ethernet driver it seems. Not an easy task.
In second mode uses a vendor specific class ID. Looking at the linux driver, it would be pretty easy to adapt one of the existing class drivers such as serialpl2303 or serialcp210x to the ipaq model. It probably would already work with the rawwrap.class if the ipaq-driver wouldn't need that special init sequence first.
And then, you're still missing the active stink protocol and the app on the other side. However, if you're willing to code the ipaq adaption, I'd gladly provide you the source to the serialcp210x.class, if you want to write an ActiveSync app, too.