edit: Can someone please explain why this is being downvoted? I'd like to make sure my contributions are constructive.
If I started a fruit distribution company and called it Rhombus, there probably wouldn't be an issue.
I can't say whether there is definitive trademark infringement here (Cube seems to offer analytics services and targets a niche market, differentiating its product). However, I can't help but feel that "Cube" is a reference to Square.
"Oh look we're going to be marginally competitive to Square, we're going to offer more than Square.. CUBE!"
No. It's an unoriginal, hackish name, but at the end of the day it looks like it could be a decent product.
It is a very legitimate point as there have been examples of similar sounding names in the same industry counting as trademark infringement.