No. We have never required that members of the community operate under their legal names within the community. Your profile on NaNoWriMo.org will display as it currently does, as will every other aspect of your public persona. Your legal name won't even be entered into the NaNoWriMo.org database. We have no reason to add it. The only file that the organization will retain that shows your legal name will be your ML agreement, which you are required to sign using your legal identity.
Signed ML agreements will live in our company files and will be treated as sensitive. It is standard for volunteer information to have similar confidentiality as human resources files to the extent that most volunteer applications contain personally identifiable information.