I just wanted to share my most recent experience with this. I used this method earlier this year to tether and it has worked great until now. I just received a letter from AT&T informing me that I must remove all tethering apps, which I had no other except this apk in place, or they would upgrade my plan to a tethering plan at the end of this month. It appears AT&T found a way to track this method, or they are assuming tethering is taking place due to high data usage during the last billing cycle.
I just wanted to share my experience and thank everyone for the help, it was great while it lasted!