Appropedia has a different approach to permissions for editing and viewing different pages. Mainspace pages have the advantage of open editing, making it easy for anyone to contribute. Original namespace documents are protected, and can only be edited by admins (and certain individuals given special permission when helping in porting, and/or the authors).
Mainspace pages have the advantage of open editing, making it easy for anyone to contribute, similar to Wikipedia.
Original pages
Private pages
It will possible to set up private pages once the appropriate MediaWiki plugin is installed. Users can gain access to these pages once they are added to a list.