Open source, as a concept, is misunderstood and thus underestimated.
Most people think that open source means Linux. It doesn't. There are true open source Linux implementations (like GNU Linux) but there are also Linux implementations that would never be considered open source by open source advocates.
Open source also goes beyond Linux. For instance, there are many Java open source projects. As with Linux this can lead to confusion. Sun's Java is not true open source, because you can't get at the source code.
For many people, this spells opportunity. Real Methods, for instance, sells a framework used to simplify the delivery of J2EE applications. It is not itself open source, but can help you deliver open source Java applications.>
oint is that the open source ecosystem is more complex than outsiders make it out to be. There are real opportunities to create proprietary software within the open source framework, and make a living at it.
You can, too. Just don't be surprised if, when you succeed, you are misunderestimated.