From the comments in that thread, one can find the other side¹ of the story:
> The first release of GNU Emacs (numbered 15.34) was in 1985, and still incorporated some of Gosling's display code. The dispute continued, with Unipress announcing that it wanted to "inform the community that portions of the GNU Emacs program are most definitely not public domain, and that use and/or distribution of the GNU Emacs program is not necessarily proper." This was countered by Fen Labalme and others who claimed that Gosling had included their code in the sale to Unipress.
> Stallman solved the problem in characteristic fashion by announcing:
> > I have decided to replace the Gosling code in GNU Emacs, even though I still believe Fen and I have permission to distribute that code
Wikipedia gives the first release of GNU Emacs was in March of 1985. In that version of the story, at least, all of Gosling's code was gone by August.
That brings me so much joy. I thought gcc was the origin point. That the initial transmission vector of GPL software was emacs is wonderful.