Yes, the actual USBHost library is based on USB Host v2 from circuits@home!
We tried to keep the original API as much as possible, since a lot of USB Devices are supported, and a lot of 3rd party libraries was built on this API.
BTW only a minimal part of the library was ported, most is still missing, for example the mass storage support.
USBHost is licensed under GPL, so if you use it on your product you must release your code GPL as well.