Joel Warren , Designer & Strategic Marketter at Wiild Interactive
Generally it means to replace references to WordPress in the admin, i.e. login screen, admin bar etc.
Some website designers use this, I update the logo on the login screen but refrain from trying to "hide" WordPress as I value WordPress and what it allows me to do.
Jennifer Lancaster , Owner at I Want That CRM
I believe this means to sell it on to clients so that they can use it under your brand (not the actual builder). e.g. WebPresences develop sites for website designers.