It depends on how you want to use the logo / in what context it would appear. The GS lawyers don't read this forum, so you'd have to contact your reseller for an official statement and permission if you are concerned.
@Karl: thank you for helping to answer this question too!
@andras: although I am not a lawyer at GS, as an online marketing professional I am also dealing with some aspects of our trademark issues too. Therefore what I can suggest is that beyond considering the general concepts and rules of using other companies' trademarks (as Karl mentioned), first of all I would recommend to read through our Trademark Usage Terms: http://www.graphisoft.com/info/legal/trademark-usage/ and when you are still in doubt, do not hesitate to contact your regional reseller or the mail address listed at the bottom of that page.