Mozilla to help Internet Explorer?

I saw this over at Slashdot (yep, I still visit this site):

An article on Ars Technica reveals Mozilla’s intention to create and release a plugin for Internet Explorer that would allow the often-criticized IE to utilize some of the cooler rendering code developed for Firefox.

I then scoot over to the Ars Technica article to see what was the Mozilla initiative all about. I learn that there’s a project for a plug-in for the Internet Explorer browser that “fixes” the rendering of the oft-maligned browser.  The article describes it further:

This Canvas plugin is only the first step toward bringing standards-based web technologies to Internet Explorer. Mozilla is working on a much more ambitious initiative called Screaming Monkey that will make it possible to plug Mozilla’s entire next-generation JavaScript engine directly into Microsoft’s web browser. If these plugins gain widespread acceptance, it will empower web developers and give them the ability to target web standards and not have to compensate as much for Internet Explorer’s broken behavior.

Wow, I really like the sound of that. But from a strategy point of view, why would Mozilla just let users download a plug-in? Will this harm the momentum Mozilla Firefox has gathered in getting market share from Internet explorer?