To be pedantic: even if there is code from MSHTML.dll in Spartan, there's no code from NCSA Mosaic in MSHTML.dll. Internet Explorer originally licensed Spyglass Mosaic, which licensed the name (and the code) from NCSA, but did not actually use any of the code. Though I suspect that there's not actually any Spyglass Mosaic code left in IE these days.

(Edited, I said that there's no MSHTML.dll code in Spartan. That I do believe exists.)

(Source: http://ericsink.com/Browser_Wars.html)