Marcus Downing

Sometimes you want the different sites on a multisite network to share their taxonomies. 
This plugin forces a child site to use its parent’s taxonomies instead of its own.

MU Central Taxonomies

On a multisite network, this makes a child site use the main site's categories and taxonomies instead of its own.

George Pattichis

Simple CPT is a free WordPress plugin that lets you create custom post types and custom taxonomies (eg: categories, tags, etc.) directly from your admin dashboard without writing a single line code.
No more editing files manually. With Simple CPT you can create a new Custom Post Type in less than 1 minute.
This plugin is written using only native functions, included in WordPress core, so it does not in any way reduce the performance of your website and will not cause any compatibility problems. Simple CPT is completely free, it will save you time and it is compatible with almost all themes and plugins out there.
In just a few minutes you can adapt your WordPress site to any type of project in a professional and extremely efficient way, e.g. ecommerce, hotel, restaurant, events, portfolio, community websites etc.

Simple CPT

Simple CPT provides an easy to use interface for registering and managing custom post types and custom taxonomies.

MU Central Taxonomies vs Simple CPT