Redsys is the Servired / Sermepa successor a leading payment gateway in Spain and European countries.
The plugin integrates J2Store with Redsys. To use this payment gateway, you will need to contact with your bank and the Redsys Gateway.
The plugin supports banks including - La Caixa, Banco Sabadell, Caixa Penedes, Caja Rural, Unnim, Deutsche Bank, Cajas Rurales, Barclays and more. Full list can be read at this page
The plugin comes with a Documentation PDF, which you can download after purchasing the plugin and then going to My Account -> My Downloads
A license entitles you to 1 year of updates, downloads and support from the date of purchase. But you can use this plugin as long as you wish. The license is for support, downloads and updates.