[jcranmer]

The success of Linux over BSD has more to do with a lawsuit in the early 90's over whether or BSD infringed on Unix's source code, which made Linux the only viable open source Unix-like operating systems if you had to ask a legal department the question.

Look beyond the OS, and much of the tech stack is dominated by non-copyleft open source projects. Both the major web servers--Apache and nginx--are permissively licensed, for example. Your SSL stacks are largely permissively licensed; indeed, most protocol servers seem to me to largely be permissively licensed rather than copyleft.

And I should also point out a clear example where copyleft has hobbled an ecosystem: Clang and LLVM have ignited a major compiler-based ecosystem of ancillary tools for development such as language servers. The gcc response to this is... to basically do nothing, because tight integration of the compiler into other components might allow workarounds that release the precious goodness of gcc to proprietary software, and Stallman has resisted letting emacs join in this revolution because he doesn't want a dependency on non-copyleft software. An extra cruel irony is that Clang appears to be an existential threat to the proprietary EDG compiler toolchain, which would mean it took a permissive license to do what the goal of the copyleft license was in the first place: kill proprietary software.