If you purchase it along with the license, you will gain access to a download of xenForo that already has the brand removed.
Also I think it's worth noting there is no true way to brand remove just about most things.
- You can still see "xenforo" in the code source.
- You can still see "xenforo" in the url or code source url of some images depending on locations.
- And it's worth noting a lot of developers that make these add-ons brand themselves as well as xenforo with or without even realizing it. For example, one says, "Some xenForo modifications by X" which brands the author of the mod and rebrands the forum you just paid to unbrand.
You can alter the text to remove the xenForo remarks, but even then, if someone does click on an Author's brand, chances are the Author's website is still branded or they're going to have a big "XENFORO" sign right on their door step which in turn, rebrands you too.
I paid for the brand free license and due to the branding everyone else has, I wish I hadn't because now I'm either very picky about using add-ons that the Author brands or I spend a lot of extra money to pay for the brand free version of that add-on.