First of all, I do it anyway. I constantly promote the MDC resources when ever I write a blog or forum post about some JavaScript thingie.
Secondly, the MDC site itself is not a perfect guide to JavaScript. Just look at the main page - https://developer.mozilla.org/en/JavaScript - it's overwhelming. Even though I use it frequently, it still makes me feel lost. Plus it has the same academic feel as W3C pages, and you know what... HTML spec is not the first result in google for "html" either.
Compare all this to the w3schools page on JavaScript: http://www.w3schools.com/js/default.asp It might not be teaching the best practices, but it sure as hell is a lot clearer than the MDC page.
Therefore I would suggest that MDC guys follow the first rule of SEO: just make a better site.