That sounds like copyright violation. See if you can find a legit free source instead.
I disagree on copyright part. Two reasons: 1) You are not selling the agreement 2) It is impossible to find out from where or whose agreement (most of them are generic). Moreover, who the heck reads those!!! I am tempted to write in my ToS - that the users hereby agree to sell their soul for using my website :) I agree on finding a legit free source.
How does selling it, whether it can be found that you copied it, or whether people read them affect that it's a copyright violation? It's a copyright violation if you publish it as your own, irrespective of whether people read it or find out that you plagiarized it.