As someone who has been paid to work on OSS, let me say that it is absolutely not about skill. Most notably, Google and Mozilla pay plenty people to work on Firefox and Chromium. Even Apple has some OSS projects (Webkit and Darwin come to mind).
It was a bit tongue in cheek - I have actually had paying gigs working on open source in the past. But the point about where the money comes from stands - Google's money comes from their proprietary stuff. I actually think something like Google is a pretty good way to produce open source software, by the way, but it's made possible by the money made elsewhere.
If I get it correctly, your point is that one requires copyright for open source software to be viable, by opening up a revenue stream to support the (free) open source part. This is true.
You can make money form open source on either:
1) Selling alternate, source closed licenses. (MySQL for example) 2) Selling support, consulting. (Red Hat, many others)
(1) requires copyright. (2) maybe less so, but without the open source licenses, which require copyright law to work, the software wouldn't exist to begin with either. Red Hat uses trademarks (which really are similar to copyright) to reinforce their position. So does Mozilla.