You are doing the right thing by researching a product before using it. Browser extensions, in particular, have more access than standard websites to your channel so it's very important to research the credibility of every extension that you use before installing it!
The simple answer is no, TubeBuddy does not violate YouTube's TOS and no, your channel cannot get suspended for using TubeBuddy.
We have a strict stance against anything that might be considered even remotely against YouTube's policies. If a user requests a feature that we feel YouTube wouldn't endorse, it is immediately denied. There is no selling of views, no sub4sub, no automation when it comes to posting comments, sending messages, etc. Nothing "black hat" or even "grey hat" for that matter. Just useful, YouTube approved tools to manage your channel better.
TubeBuddy is used by many top YouTuber creators and YouTube experts every day and they love our product. TubeBuddy has been used by 3+ MILLION YouTubers since 2015 and has nearly a 5 out of 5 star rating on the chrome store with more than thousands and thousands of reviews.
Feel free to email us if you have any specific questions or concerns and we'd be happy to answer.
The TubeBuddy Team