But BSD init is more horrible in this regard: by using shell script, it is easy to incorporate proprietary code into an otherwise copyleft product. The propone

But BSD init is more horrible in this regard: by using shell script, it is easy to incorporate proprietary code into an otherwise copyleft product. The proponents of the "UNIX philosophy" that try to define the latter as writing lots of independent tools that can be combined in shell scripts, are probably just trying to make sure they also can work around the GPL in the future too. That's why the gcc compiler suite doesn't provide ways for other applications to access its AST via stdout: it could be used to code completion in emacs, but also to write proprietary gcc addons that manipulate the AST and work around gcc's GPL license.