I'm completely fed up by people not remotely connected to BSD telling the world what the lesson of BSD is. You've entirely missed the point.
The purpose of BSD is to be re-used, by anyone, however they want to use it. This includes companies that want to take it away and don't share anything back - although, companies like this don't exist. Even the most evil of all evils, Apple, contribute back a huge amount of work they do on FreeBSD and FreeBSD related technologies.
FreeBSD is the base for many closed source OS, typically shipped on appliances like IronPort. Guess what? These guys collaborate amongst each other, contribute fixes upstream, and even suggest architectural improvements based upon their experiences.
Yes, BSD allows rampant copying of source code and relicensing, and anyone can use it for whatever purpose they want. This does indeed conflict with RMS' worldview, but its what we were aiming for in the first place.
If you don't like it, don't use it, but please, for the love of fuck, please stop telling us that we haven't learnt our 'lesson'.
PS: Agree with the article 100%. A technology is never truly free to use if there is not a free to use - for everybody - version of it. All the best, universal, technologies have liberal free licenses, eg libpng, libjpeg, openssl, openssh all have liberal licenses to encourage use of them in all scenarios, and to enhance interoperability between applications. The internet took off easily because most OS started out with a copy of BSD's TCP/IP stack.