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: 
Red Hat (and most of the other Linux vendors) charge for support, not for their software - which is primarily how companies can make money off of code that is GPL licensed.
Isn't that essentially what red hat does? Even though they have fedora, they are charging money for their linux distribution. Granted, they've written a lot of code for it, it's still based on open source-stuff.