[Zigurd]

What's wrong with that comment is that people think it is wrong for some fairly obvious reasons. for example: there is no causal link (which is also the point of the comment originating this thread). Examples of software needing to be open source to succeed, like other languages, the Android OS, etc. are easy to find.

Even your more qualified point has loads of counter-examples, that companies that did not start with their software as open source find it hard to succeed at open source: Google's search engine and much other software is not open source. Many companies mix their approach to open source with proprietary systems and products. As did Sun.

That Wolfram's justifications are weak is not necessarily a knock on their decision. But the specific point that "High-level languages need more design than low-level languages" seems particularly odd. There are high level languages where all the widely used implementations are open source and few cases of them becoming chaotic. I suppose there is survivorship bias in that observation but there are also obvious reasons why no language user community would have a lot of patience for a proliferation of variants.