I'm unclear about this license. If something is released under the GPL, and you modify it (to add features, correct bugs, etc.), then can you set the project up on sourceforge? And how much credit do you have to give the original author?

If you modify, add new features, fix bugs of a program then submit the code to the project, why whould you want to start a new one???
About the credit, you ususally get the credit you deserve.

You might want to read the GPL

http://www.gnu.org/copyleft/gpl.html

quote:
These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

There are many instances of people basing their work and code base on existing projects. However, if you just added a feature or two, or corrected a simple bug, thats not a new project. Now if you added a ton of new features that the original programmers never intented to add you probably would have the basis for a new project.

Remember though, there are many open source projects. Does yours really contribute something to the community? If not, if it's just a clone of an existing product with 1 or 2 extra features, why not contact the project leader and tell him/her that you would like to contribute some features to their code base?

Because it's a company that has released it, they don't update it often, and they charge for it.

A person can sell any gpl'd programs they want. But they would have to release either the whole program under the gpl or even if their modifications were not covered by the gpl the part that was originally under the gpl would still be so.

well, I realize that they can sell it, but he was asking why I would want to release it on sourceforge