paperrater.comは安全ですか？

There are a lot better grammar checking tools online, that you can use for free, without going thru all the stuff this site wants you to. The one I personally use, doesn't have any kind of terms of service you have to accept, and sign away your life, like you do on this site.

from their TOS: "By submitting Material to the Web Site, you agree to grant the Company, its agents, affiliates, representatives, licensors, and licensees, a worldwide, irrevocable, nonexclusive, perpetual, royalty-free right (including moral rights) and license to copy, modify, translate, publish, disclose, transfer, assign, sell, and distribute said Material in any form now known or hereafter developed, for any purpose without limitation, and without any obligation of notice, attribution, or compensation to you or another."