To be clear, the silly question I posed was not directed at avoiding copyright violations. What I ask is whether anyone is ever curious about the value of the derivative work versus the original work.
For example, the original work might be very valuable, a significant work. It could be the collective work of many authors. But it has been made available for free. The derivative work, maybe patches or some additional source code by a single author, is also valuable but on its own much less so.
Then the large original work is packaged together with the patches and additonal source code as a "derivative work". It is commercially licensed to an end user who sees the value as a whole, most of it coming from the original work, which of course was available for free.
Depending on whether attribution is given, the user may have no idea that the core of the product was open source and available for free.
More importantly, there appears to be no assessment of the relative "value" of the free portion versus the closed-source commercial portion of the product.
A patch is a derivative work, no matter how you try to dodge that part of the law. So it would still be violation of copyright.