Image-Line registration name - (e.g. ACustomer from the screenshots here), this is the name that was used to purchase FL Studio, or other products.
The name displayed in the FL Studio Title Bar when launching FL Studio is the name you registered FL Studio with. This name CAN NOT be changed.
If you are making videos and don't want your name to be shown at start-up. Set your default project to one of your existing projects. You can do this from the General Settings > Miscellaneous > dropdown window at "Startup project" > "Last used project".
Alternatively, 'Save as ...' prior to starting the video, then your name will be replaced with the project name.
NOTE: your name is always shown in the menu Help > About window:
Image Line Support Team