Question: This question has always been around my head.

Can someone create a new product based on an existing open source project?

Say you want to create an "Apaxe webserver" that is basically Apache with your some extra plugins ( say support for ASP or something similar ) 

Is this possible?

Would you be able to create a closed source product ( either free or licensed ) 

As for GPL seems clear it is not possible because the source should be open. But what about Apache license, BSD and others "corporate friendly"

Are the price ( free for most of the project ) , bug fixes and counting with the core development team the only thing that prevent from others to commercialize those OS products?

What about: Khrome a commercial product based on Chrome with ActiveX support ( who would dare to do such a thing :P )

**EDIT**

Thank you all you all for your answers. 

So, again

***What prevents from similar ( clone ) products from appearing in the market?***

:) 

NOTE: I know we are not lawyers, and we could read every OSS license here <http://www.opensource.org/licenses>.

Answer: 
Nothing prevents clone products appearing on the market. Look at all the various linux distributions, for example. The X.org project was forked from XFree86. And so on.

It happens relatively infrequently, though, for a couple of reasons:

* The original project has the first-to-market advantage
* The original is usually being given away free

So unless your version is significantly better than the original, you're not going to get much uptake or make much money out of it. If your version **is** significantly better, then go ahead!

From the original developer's point of view, the power of the GPL is that it forces such clones to share any improvements with the rest of the world, so they can be incorporated back into the original.
look at MyEclipse, its really just eclipse+free plugins+myeclipse's plugins and it cost some money.