WordPress.com allows installation of plugins only for websites in the WordPress.com Business plan. If you have free WordPress.com website, or you have paid account other then business, you can’t install plugins, and you can’t use Dev4Press plugins.
If you have WordPress.com Business plan, you can install and use Dev4Press plugins with some exceptions: Dev4Press Updater, GD Security Toolbox Pro and GD Press Tools Pro will not work. As for all other plugins, they should work fine. But, all the plugins that do work, can be used from WP Admin panel in the WordPress.com, they can’t integrate into WordPress.com own dashboard or editor.
But, due to the way the WordPress.com works, and the fact that it is a very closed system, we can’t provide support related to the server setup, and we can’t guarantee that all our plugins will work with WordPress.com as expected.