So in case anyone is making the move from OG droid to this wonderful crisp Droid 3 and was previously using PDAnet you may have had the same problem as me trying to get it on the Droid 3 and working.
I may have a unique case but I figured I'd share to possibly help others if they are in the same boat.
If you were using titanium backup on the OG droid you should have PDAnet .apk file backed up on there. Copy it off and simply load it on the Droid 3 using your PC or other method. I placed it in the internal storage download folder. Then use ASTRO or another file explorer to find it and install it. Make sure "unknown sources" is checked off in applications settings because this is a new phone (i forgot this one myself because I had checked that box two years ago on my OG droid). Install and it should be working fine using the same USB tethered method you used previously.
I tested mine out but only for a few seconds. I am still unsure if Verizon is going to monitor and pinpoint uses of this, on my OG droid i never was contacted by them and I used it fairly regularly (once a month) to help in a pinch when working on writing for my blog.
Anyway hope this helped or at least you enjoyed reading. Loving this phone.