Please note that support for NextGEN Gallery will be moved to the NGFB Open Graph+ Pro version in v6.21.0.
This will restore balance between the two versions - the GPL version has complete support for all Open Graph+ meta tags and WordPress features, including its gallery shortcode.
3rd party plugin support, like NextGEN Gallery, WordPress SEO, BuddyPress, bbPress, WooCommerce, and many more, is available in the Pro version.
I remain committed to providing a reliable and complete set of features in the GPL version - for free. There's no need to contribute in any way, though a little help with forum questions is always welcome. ;-)