CMB2 is a developer toolkit for WordPress custom fields, metaboxes, settings pages, and forms. What makes it unique in the WordPress ecosystem is that it was purpose-built to be safely bundled inside other plugins and themes. Hundreds of WordPress products ship CMB2 as an embedded dependency — and its WP Lib Loader pattern automatically resolves version conflicts so only the newest copy loads, even when multiple plugins include it.
CMB2 doesn't meet the 5K GitHub stars threshold because WordPress developers don't install via GitHub — they install via wordpress.org and Composer, or more often, they never install it directly at all. It arrives inside something else. Our real adoption numbers tell a different story.