SlickGrid - why isn't it in the jQuery plugins registry?

SlickGrid - why isn't it in the jQuery plugins registry?

https://github.com/mleibman/SlickGrid

Is it not in the plugins registry because it isn't technically a plugin?  And/or Is it because the author just hasn't submitted it?

Even if it's a technically an "extension" (or some other term) and not a plugin, it still seems like a very full-featured thing not to be listed somewhere on the jQuery website.  It's clearly been built to work with jQuery.  I wouldn't have found it if all I did was search the plugins here, and not finding it would have been a shame.