I want to create Metro apps for Windows 8, and I have VS 2012, but I need a developer’s license. If I use fake credentials, will I be able to later get a different developer’s license with a different Microsoft account on the same computer?
If I can change it later, how?
The developer account you are entering can be as far as I know independent to the real account you will use for publishing your apps.
Every time you want to create app package for uploading you’re entering your credentials, in case you want to develop under several different accounts, so yes, there should be no problem when using different account for “activating Windows 8 development” and for publishing your apps.