And I want to put ads and monetize it? Is there a problem with that since it's made for organizations or no?
Yes once you register it is yours to do what you like. Only some domains like .travel & .pro might have certain restrictions but not with .org.
The rule of thumb is to check with the adsense or groups who pay for the advertising and ask them which is their preference, and if they do bar certain .org or other addresses? Regards Andrew
I own a few .org sites and I'm monetizing the site with google ads...so, you can do anything you want with that domain.