[sschueller]

Also don't forget the satellite radio service that merged with XM radio. [1]

[1] http://en.wikipedia.org/wiki/Sirius_Satellite_Radio

[aylons]

Well, this is more distant. If we're at it, it is also the name of a particle accelerator in Brazil: http://www.lightsources.org/news/2015/02/21/sirius-%E2%80%93...

[sschueller]

It doesn't matter in the US. A large company will take you through the ringer if there is any possibility of confusion even if they may not have a claim.