Nope. There are commercial products available for Linux. Oracle is probably the best know one, though Adobe is also coming out with a Linux product.
Writing a commercial application that does not use GPL'ed code means you do not have to distribute the source code. Hence, it can be as proproetary as you like.
Most commercial linux products do rely on the LGPL license for their linkages to GPL'ed libraries. This license is different in that you don't have to GPL your own code to use a LGPL library.
Thanks. Well, I'm starting to get it.