Dear customer,
A Small Business License allows 10 such names
An IP license enables all the domains/subdomains hosted on this IP@ to use the control.
All license options are good for http://localhost. I'd highly recommend Small Business License as it's the most popular choice among our customers. Out of the 10 names, you can use one or two for the internal dev server ie. http://intranet while keep the rest for your production servers.
It's fine to use the 10 names for different customer websites, in your case, company A and B. We don't check website ownership when registering those 10 names :) Questions?
Thanks for asking