I believe ESR is wrong.

In years past, there was BSD unix, a modified version of the unix shipped from Bell Labs. The BSD changes were theoretically "free", in that if you had a license from AT&T (which were easy to get, since at the time AT&T couldn't sell software), you could do anything you wanted with them.

What people did was to fork BSD, take their modifications proprietary, and create Solaris (well, SunOS), HP-UX, AIX, Irix, and a fair-sized stack of others that did even worse in the marketplace. The end result of that was fragmentation in the Unix ecosystem, which was bad on many levels. (One example: Don't like autoconf/automake/libtool? Guess where the necessity of those came from?)

Or, how about Jordi Gutiérrez Hermoso's response to ESR:

"The FSF sure can prevent it, and proprietary compilers still thrive. Here is one that particularly bugs me as an Octave developer: we routinely see people being lured to use Nvidia's non-free nvcc for GPU computing, which they gleefully admit is based on clang and LLVM. And there is Xcode, of course, completely non-free and completely based on clang and LLVM.

"The fact that these non-free tools are not based on gcc are a testament to how proprietary software developers cannot plug into gcc, and how clang is fostering non-free software.

"The nvidia situation is particularly dire becuase today, free GPU computing is almost nonexistent. It's almost all based on CUDA and nvidia's massive pro-CUDA marketing campaign. Even most OpenCL implementations are non-free, and the scant few free implementations of OpenCL that exist are not fully functional."

So we have several examples of ESR's approaches failing. On the other hand, the GPL does a pretty successful job of preventing the kind of fragmentation that damages ESR's "hacker community". And part of the reason it does is the FSF's dogmatic stance.