I'm all for utilizing resources given to you, but I would think about asking a systems administrator or other such person before jumping into this endeavor.

I agree that it's nice to fly under the radar. But if you don't feel comfortable talking with them about it, i.e. if you are unsure whether they will be cool with it, keep in mind that they will probably find out and, regardless of your interpretation of the usage agreement, probably have the right to get upset.

And if they are cool with it (or they want to take a cut, hehe), they may be able to provide you with useful information or assist you in some way.

But if you don't want to tell them, I still say go for it anyway!