Red Hat, the world’s largest provider of open source software, would begin to reserve the source code of its flagship product, Red Hat Enterprise Linux, to paying customers only.

I think they should have done that in the first place. You can sell open source software just fine; you shouldn't be expected to make the sources public—only to those with a binary copy of your software who ask for it. Organizations that write and maintain open source software should be paid for their work.

In 1984, a researcher named Richard Stallman released a software project called GNU. Stallman licensed GNU for free, with his only stipulation that users sign an agreement called the GNU General Public License. [...] To Stallman, freedom meant no restrictions — not necessarily no costs. “Think free as in free speech, not free beer,” he is quoted as saying.

Yes. Stallman sold copies of GNU Emacs on physical media back in the day.

This article doesn't touch on the contentious issue, which is that RHEL's terms say, if you share the Red hat sources as a customer to a non-customer, Red Hat may stop serving you as a customer. The controversy isn't about cost. It's about being punished for exercising the freedoms Red Hat gives you.

Of course, SUSE and Ubuntu Enterprise have had the same terms for years. Red Hat was the outlier until now.