All Dev4Press free and lite plugins can be translated via WordPress.org and their translation services. Each plugin on WordPress.org has support for translation, and you can get to it through the plugin Developer panel. To translate plugins on WordPress.org, you need a WordPress.org account. But, if you want to handle translations on your own, each plugin has a POT file with the list of all translation strings
Yes. Each site in the network can activate and use the plugin.