I inquired to them and got this answer back:
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yes, it is a legitimate offer. We were caught off-guard by PC World releasing
their magazine a bit early (the free offer is an ad in PC World), so we put up
the readily available Office 2008.
It will be replaced by SoftMaker Office 2006 in about one hour.
Best,
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And checking again, the page was indeed updated
Now since I downloaded it a couple hours ago, I have Office 2008 .exe. It scans clean.