Having looked at parts of the Office source I would be extremely surprised if this is anything but a statement to placate OSS devs. The sheer amount of effort required to port Office to Linux would be a few orders of magnitude greater than any sales that could possibly be achieved from Linux users.
They've been able to port various Windows-centric products to other platforms before (to Mac and Solaris at least). Exchange, Office, Internet Explorer etc.
I agree they won't make a huge profit from it directly but I bet it's a good counter-argument to "let's standardise on OpenOffice since otherwise we are subject to MS vendor lock-in". A couple of big government or corporate deals should cover the costs.
