The Joomla! 2.5 and 3.x versions of the Only Once! plug-in have been renamed Login One!
Visit the project website for the J1.5 version.
A nifty plugin that prevents duplicate or multiple log-ins by the same user credentials, for both front-end and back-end. A useful tool for websites that share or exchange potentially sensitive information amongst their registered users.
User must either sign off the first session, or wait until the first session has expired. Super administrators can always have multiple log-ins.
There are two plugins that must be installed via the Joomla! back-end. See instructions in the download package.
Supported languages: Frontend: Dutch, English, German. Backend: English.
Premium and Business editions are available, offering more sophisticated options.