You can not generally share a file using only a Runtime version of the database. Runtimes are single user only.
The exception is when using Filemaker Server, which can host runtime solutions.
Using Filemaker Pro or Advanced, you can share a database with up to 9 Filemaker users and up to 5 web users using Instant Web Publishing.
EDIT: in retrospect, after rereading your post, I am not sure I hit the mark on your question.
If you are asking if it is possible to have 5 user accounts in the file after removing admin privileges, the answer is yes.
You need Filemaker Pro Advanced to remove admin privileges from a file. This option will delete all accounts that use the Full Access privilege set, but leave other accounts unchanged. This will also permanently remove access to Layout mode, ScriptMaker and Manage dialog boxes, making it impossible to alter the structure of the file afterwards, even when using Filemaker Pro/Adv.