It would be very clear to a lawyer what "in the course of a commercial activity" means. And accepting open source contributions from a business entity normally isn't considered "in the course of a commercial activity". (It's like buying apples from the supermarket is not a engaging in commercial activity on the part of the customer, even if the supermarket is.)
No disrespect to the author, but even consulting with a law student would clear up the issue. Maybe better access to law would be nice, but if the OSS community is really concerned with this issue some lawyer would have clarified this already.
IANAL of course, and this is not legal advice.