This is highly jurisdiction dependent so for anyone to give you an answer we would need to know where you are.

I'm going to assume the US for no other reason than that's where I'm sitting right now. If that's the case you can find some info here:
http://law.stackexchange.com/a/1857/10044

That answer is to a question about website footers but the answer should be informative anyway.

The site I linked to, http://law.stackexchange.com, has a lot of good info relating to software & copyrights. Most of the respondents on the site are lawyers. Of course, anyone on the internet can generally make whatever claim they want regardless of reality. For example, I'm the world's handsomest rocket scientist and also a Highlander... In general most of the answers given will refer to relevant statutes and you can look them up for yourself if you're concerned about anything. Most of the time if somebody gives an incorrect or incomplete answer, somebody else comes along in short order with a correction or more complete answer.

Take a look there and I'll bet that you can find the answer to your question. If not you can always post a question of your own. But copyright questions are pretty common there, so I'm guessing you could find all you need by searching.

Editing to add: My original post might not have been clear - the answer I linked to is US specific, but the site is not. So if you're in a non-US jurisdiction you can still look for answers there and post a question if you'd like. They use tags on questions, so look for a tag corresponding to your jurisdiction when looking at questions. And if you ask one, be sure to add a jurisdiction tag to it as well.