The whole point of this is while you guys are arguing people on youtube ARE making money, whether it be a lot or a little. This guy has figured out how to get the most ad clicks/watches without having to make some dumb video to get 1 million views. If the ad correlates to the video he’s going to get more ad clicks than someone who made a frozen parody that has an ad about car insurance.
You can't use copyrighted music in your videos unless you can prove you are the owner of the copyrighted material. If your account has too many "copyright strikes," which are instances where you've been warned by YouTube about having copyrighted material in your videos, then you will be banned. If you are using public domain music in your videos, make sure to give credit to the creators of the material in the description, if applicable: for example, Sneaky Snitch by Kevin MacLeod used with permission. That way, everyone gets acknowledged fairly and the freedom of the intellectual property commons thrives at the level of community.
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.