[BrendanEich]

I was a cofounder of MDN (originally "DevMo"), and we did not use Opera or other materials, we used Netscape's DevEdge content which was released to us. You may be thinking of a later reformulation to unite with others outside Mozilla. See

https://developer.mozilla.org/en-US/about#our_journey

[mananaysiempre]

Sorry, I probably did not phrase that well: I did not mean to imply that (what ultimately became) MDN was built on others’ materials. Rather, my impression was that other browser developers had agreed on taking down their own web documentation in favour of directing people to MDN, and that the Opera course (itself quite new at the time) was among the casualties.

Checking the Wayback Machine, looks like my subjective time was quite warped then: I had read the course around 2010 (which was actually called the Web Standards Curriculum[1,2], oops) and was sure it had been memory-holed with a redirect to MDN (along with the rest of Dev.Opera) when Presto was still alive (so before 2014), but it turns out that that did not happen[3] until 2018, matching your timeline.

[1] https://web.archive.org/web/20100119040913/http://dev.opera....

[2] https://web.archive.org/web/20111128034924/http://www.w3.org...

[3] https://web.archive.org/web/20171013125336/https://www.w3.or...