Can anyone just use the logo of Bitcoin without copyright infringement? As far as I know this can already be in the Creative Commons category but if you can get that special permission then much better. Or you can also modify a little and add something to the logo to make it on your own. The whole Bitcoin community will be happy to see many people using the logo to be emblazoned on any product as this can be like a free advertising for the coin. Since Bitcoin do not have an organized and centralized marketing department with a multimillion budget, mentions and uses of the logo on different products or events can be helping a lot in promoting its name and popularization of the very idea which Bitcoin is standing for.