I'm the developer of this app, so thanks to the OP and to Android Central for helping to publicize it, I really appreciate it!
I have never heard of any user incurring charges from the carrier for using this app.
On some phones, with some carriers, there is software that redirects all traffic to the carrier's home page, encouraging you to sign up for the hotspot plan, but if you don't choose to sign up, then they don't bill you.
From what I've been told, this app works fine with Galaxy Nexus (traffic is not redirected).
However, it is always possible that some time in the future, a carrier may block the app.
Happy Holidays,
Doug
Search Android Market for "Wifi Hotspot and USB Tether" by SVTP or follow these links:
Paid Version $9.99 - 5 day money-back guarantee
https://market.android.com/details?id=com.svtechpartners.wifihotspot
Free Trial - 2 days
https://market.android.com/details?id=com.svtechpartners.wifihotspotdemo