What? Umber is just a preposition, it doesn't has nazi overtones. The fact that it's grammatically incorrect is probably a plus, because it's then less likely to be confused.
If you use "über" to describe something as better in some way, nazi overtones are very obviously present and if you name a company Uber, it's definitely implied that you're better than the alternatives.
Wasn't this the point of the name?
Where I live people use über often and it means pretty much what it means in German and has no Nazi connotations. (Of course most of our German ancestors moved here long before WWI)