The jalert application is just a wrapper around the j:alert procedure in the jalert.tcl library. It's intended to make the functionality of j:alert conveniently available from shell scripts.
This help file describes jalert version 4.0/4.0.
Copyright and contact information is available in the jstools documentation.
jalert [-title title] [-text text]
Invoking jalert causes a panel to appear with the title title, displaying text, with an OK button. When the user clicks OK, jalert exits.
Both title and text are localisable.
For more details, see the documentation for j:alert in the jalert.tcl library.
* It might be nice to be able to force the window to be centred regardless of the user's preferences (or lack of them).