Also welcome to wikitree from me! As Jan has already told you, a project for Belgium is being set up. If you're interested in joining, just let me know here or as a reply to this question!
@David: for the practical and historical reasons that Isabelle, Jan and Andrew have already given, the Belgium Project defines its scope as "the geographical area that is now the country of Belgium", so including profiles from before 1830. Both the Dutch and French projects fully agree with this. Of course we'll collaborate closely with those projects and make sure all guidelines, categories, etc. are compatible!
That said, at this moment the Belgium Project is not yet a project, so for the time being "official" project-management and project-protection is mostly covered by the Dutch or French projects (depending on the situation).