Folks that mindfully contribute BSD- and MIT-licensed software do not share the perspective that they are performing unpaid labor for corporations.
I personally regard copyleft as a severe curtailing of options and equate it with being forced to adopt a narrow, ideological worldview. Worse, the GPL perpetuates the fundamental atrocity of intellectual property law, by hacking it, and therefore intrinsically depending on it; in contrast, the BSD and MIT licenses are mostly a liability waiver under an assertion of attribution, ultimately creations more of necessity than ideology.
In the context of abjuring exploitative corporations, I hear an echo of trade unionism, a movement often oblivious to its own reinforcement of capitalism, again by depending upon the thing it purports to confront; few entities are more aligned with the moral sentiments of Adam Smith than a trade union engaged in collective bargaining. And so it is with the copyleft licenses and their implicit support for enforceable intellectual property rights.
The article linked appears to be derogatory, emotive, riddled with false equivalences, and relies on invective as a substitute for rhetoric. Rather than finding it compelling, it think it describes a myopic, narcissistic view of both intellectual advancement and the value of unfettered contribution.