I think you should be able to set the “CreatedByID” value to the proper user instead of administrator and that should do the trick as far as I can tell. To locate the user ID’s you can look at the “Users” table under the “UserId” column in the OnTime database which will give you the correct ID for the desired user in the database. 

This is an OnTime 2007 SDK Example which shows how one can import MS Project Tasks into OnTime as OnTime Tasks or Features.