Naturally, it is easy to misinterpret statements, such as you read in terminal. Your 'dropbox start' statement, in fact, started Dropbox to running in the background! and the 'done' part of the statement only served to affirm that it is now running. The earlier part of the statement indicated that yes, dropbox start is a welcome order due to the fact that it is not yet running. Very simple, also very simple to misunderstand.