Tube Toolbox has been the leading YouTube Marketing Software since 2007. One of the primary design guidelines followed since the beginning is that we would build a product that has complete compliance of YouTube's Terms of Service. It was in our own best interest because otherwise we would face getting shut down by YouTube ourselves.
We have thousands of customers using our product on a daily basis (including MANY YouTube Partners), some of which have been using the product for the entire 6+ years we have been in business.
We do not "sell views" or "sell subscribers" or give you fake "thumbs up" on your videos. We don't do anything to artificially skew the data on your account or YouTube's site. All we do is automate processes that you could have otherwise done manually.
All that being said, some people create a separate account to use for marketing through Tube Toolbox. They use this account to send messages and reference their primary account. This provides an additional level of protection for their main Channel for those of you who are ultra concerned. Read about multi-account sending here.
THE BOTTOM LINE: YouTube will not suspend your Channel simply because you use Tube Toolbox. They can however, suspend you if they feel like you are spamming too much - and it doesn't matter if you are using Tube Toolbox or doing your sending manually. What is "too much"? There is no definite answer but we have implemented a Risk Level feature which helps guide you in the right direction based on the experiences of our thousands of users and our 6 years in the business. If you stay in the "Low Risk Level" of using Tube Toolbox, you should be perfectly fine but as in life, there are no guarantees. Most customers are fine even when we tell them they are 'high risk' because we want to error on the side of keeping you safe. We wish you luck in your YouTube career!