For starters, I recommend the book "Open Source Licensing - Software Freedom and Intellectual Property Law" by Lawrence Rosen, legal counsel to the Open Source Initiative.
Of course, some of his views contradict those of the Free Software Foundation, but yeah, "infinite are the arguments of mages".
GNU does pretty much, exactly that it just uses legalese as any good contract should
Though the GPL is a bare copyright license rather than a contract, since there is no acceptance required.
Oh well.
and i would never promise any kind of exclusive license to EvilCorp for stuff that was in the public domain.
You cant even license that which is in the public domain to begin with.
While software in the public domain can be considered Free/Open Source software, Free/Open Source software may not (and usually isnt) in the public domain.
i guess my question was more "can I make a proprietary offering based on my open source project"?
Yes, with a dual-licensing scheme, assuming that you hold the copyright to your project's software.
When more than one developer contributes, things can be a little more difficult since it isnt just your copyright that is involved, unless the copyrights are assigned to you, or some other agreement is made.
Actually, if this is the case, you probably could release your project under any OSI approved license, since they all should fulfill 1-3.
Of course, what exactly you mean by "credited" isnt clear, while #1 doesnt even need a license to do this for you, a copyright statement would be enough.
Aside from the GPL, LGPL, (modfied) BSD license, MIT (or Expat) license, and zlib/libpng licenses, I would suggest that you take a look at the Academic Free License and Open Software License.
Disclaimer: I am not a lawyer, this is not legal advice/opinion.