I may be mistaken, but the database is open and being shared by a server.
The database is locked in several fashions.
You can not change the structure unless the database is closed.
You may not change the structure even with admin permissions from a remote computer.
There are basic security measures to prevent data corruption.
I agree that it's generally a bad idea to make structural changes to your database while it is "live". Editing a table's schema, for example, can result in locking the table when other users or scripts are attempting to modify data in the table and that can get ugly real fast.
However, I can easily do so if I open the hosted database with a full access password. I don't use active directory and haven't tried such an install option as described, so that may be the cause of the problem here, but modifying a hosted file's design can be done. I sometimes do that after hours when there are no users connected to the file.
Layout modification, on the other hand, is pretty safe though an unexpected change in layout appearance/behavior might confuse your users.