[SloopJon]

> it will be incorporated in a company's proprietary project thus lowering the expenses necessary to develop it

Without necessarily taking a position on the ethics, I would point to macOS and its derivatives as a clear example of this. Apple invested significant resources into a successor to System 7 called Copland, abandoning it in 1996. While the purchase of NeXT in 1997 hugely influenced the design of OS X, look at all of the free and open source projects that accelerated its development: Mach, Clang/LLVM (and GCC before it), KHTML, KJS, CUPS, much of the BSD and GNU userland, and the list goes on.

macOS, and by extension iOS, would not be where it is today without its open source core. Put a little spit and polish on it (no small thing, of course), add a kernel extension named Don't Steal Mac OS X.kext, and voila: new O/S.

[favorited]

The flip side (of this specific example) is that several of those projects were either started or nearly exclusively funded by Apple.

- Mach's primary architect, Avie Tevanian, was hired by NeXT to productize it, and he continued that work at Apple with XNU and the OS X strategy to replace the classic MacOS

- Apple hired Chris Lattner after he finished his PhD (where LLVM was started) and then created Clang and open-sourced it, as well as other LLVM tools like libcxx

- Apple hired Michael Sweet (creator and maintainer of CUPS) and paid him to maintain it for several years

As you say, Apple's software wouldn't be where it is today without open source. But major open source projects either wouldn't exist at all (e.g., Clang) or would have needed someone else to pay for their maintenance (e.g., CUPS) without Apple.