If we are notified by a copyright holder that someone has published a project with their music without permission, we are legally required to take down (unpublish) the project, but provided we do that, we are explicitly safe from a lawsuit, according to the Digital Millennium Copyright Act. The copyright holder has to take the initiative; we are not required to monitor all projects our users publish. Look for "DMCA" in that forest of links at the bottom of the start page for more details.
That's in the US. I'm not sure about laws elsewhere.
All this applies only to published projects; you can use any music you want in private projects. IANAL, but I believe that for projects that you share but don't publish, you're the one doing the distributing, not us, so if anyone's in trouble it's you. If you share a project and post the URL on the forum, then we're in DMCA territory.
P.S. It's spelled "copyright," as in the right to make copies of something.
No, we are responsible for responding to DMCA takedown notices by unpublishing the project. If we were Facebook or Twitter we probably wouldn't even tell you we had done so, although you can appeal a takedown once you find out about it.
So far, knock on wood, we haven't had any. We're too small for anyone to bother with. Scratch does get a few.
There are a lot of pirated software.If you really really reallllly want to care about copy right,care about that first.The authors will not have time to pick your copywrong and tell bh in most of cases.
(you cannot get a lawsuit this way bc bh will unpublish or delete your project before the authors get supra dupra angry)
I don't think that makes it okay, but if your work is considered 'transformative' enough under the law, then it can be considered to not infringe on copyright. (I'm not a lawyer so I'm not entirely sure.)
In at least some European countries they divide rights into copyright, which has to do with the right to make copies, and "moral right," which is the right to be credited as author, the right to insist that modifications of your work be clearly labelled as such, and so on. You can, and authors routinely do, sell the copyright in a work to the publisher, but you can't sell the moral rights. Those are attached to the actual author for life, and then to the author's literary custodian (as specified in a contract signed before death (obviously)).