— Yes free product is possible.
— Not possible. Woocommerce handle it.
— If you use wpml then it is ok..
–Yes only for Woocommerce but we are working for Easy Digital Download and we have no plan to develop for Joomla!
It's perfectly secured. WooCommerce creates a separate folder in your WordPress upload directory and protects it's access via .htaccess rules and also the url's aren't shown anywhere. Users get encrypted download links and only he/she can download with that download link. So it's very secured.
My apology on this. By-default WooCommerce is secure and it uploads to it's own directory for more security, while we've skipped their upload folder in Dokan by mistake. We'll fix it in next update. But, if you turn off indexing on uploads folder (which is ON in our case), it won't show.