The article also singles out the GPL repeatedly as a source of contamination. It doesn’t mention source-available proprietary licenses. It doesn’t mention code put online with no clear license, which according to the Bern Convention and the laws in at least the United States is automatically copyright protected with no license for use by others at all. It doesn’t talk about attribution for BSD-style or CC-SA-Attribution licenses. There’s no mention of leaked proprietary code. It just singles out GPL as some sort of unique problem.
This seems quite shoddy and biased for an article by someone who’s writing about the law.