Can i get charged for using PDANET?

I have 2 HTC EVOs 4G, and a Samsung Intercept- all from sprint- all with Android. Will i get caught if i used PDA NET on my phone/ desktop and cancel my cable service? My cable company is charging $85+ per month... It will save me a lot of money... Can Sprint catch me for tethering on my phone with PDANET? (its a free app, and Sprint doesn't get more money) I heard AT&T and VZW you can get caught, but what about sprint?