It could very well be that I'm tired and missing something, but I don't see where it says that in the TC article. And I don't personally run Firefox, so I can't go through the pages of designs on the page linked to in the TC quote to verify this myself.
FTA (emphasis mine):
Mozilla is now aware of a post by MetaLab that shows a Mozilla developer copying prior design work. The mockups they cite were an early proof of concept created by cut-and-paste, never final designs. Mozilla respects the hard work of all designers and at no time meant to plagiarize original content. The in-progress designs for the Jetpack SDK’s IDE are available here and following initial sign-off on the proof of concept, the IDE was developed entirely independent of MetaLabs’ work.
