Even though selling software is perfectly in line with GPL, since 99% of FOSS has not been commercialized, people have gotten this idea in their heads that it's wrong and antithetical.
Even though (regarding collaboration) the only requirement of FOSS is to make the source code relatively easily available, people have been accustomed to the GitHub way of developing for so long that it has forever changed the perception of what is considered an open source project
> “Free software” means software that respects users' freedom and community.
(my italics)
This is why, while 'FOSS' can sometimes serve as a useful, rough grouping, the need to distinguish Free Software from Open Source is an important one. The two are not the same. The author of the submitted piece, of course, talks only about Open Source.
[1] https://www.gnu.org/philosophy/free-sw.en.html#four-freedoms