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This Matt Cutts video is from 2013, but I think it still applies today. I ran into the same issue once re: terms & conditions, asked a question very similar to yours, and somebody on this message board shared it with me. Hope it helps. Long story short, as long as you're not being spammy about it, you should be fine. I would add that since it's actually useful to your user, I would implore you to include it!