The SFTP license reminder only pops up for every 10 operations you perform on an unlicensed copy. If you are getting the popup, it is because you are using the plugin!
The current popup verbiage is:
Thanks for trying out Sublime SFTP. It is free to try, but a license must be purchased for continued use. Visit http://sublime.wbond.net for a license.
If you do have suggestions about something that would be more clear, I would be happy to listen.