Domain Taxonomy | drupal.org

This module extends Domain Access (DA) functionality to taxonomy objects. It makes taxonomy terms dependent on domain access rules like nodes. In practice, it means that term editing forms are extended by new options for choosing domains where term must be published. This options block is identical to the block for nodes from DA, but have some additional features for allowing inheritance of domain rights to child nodes or terms.

And when you create nodes with term which have assigned domain right, than term right inherits to this new nodes.

Filtering of terms list for current domain is organized by proccessing db_rewrite_sql hook on taxonomy select queries.

This module useful for many other modules, like Forum which can excellent work with DA module on nodes (topics) listing level filtering for domain accessibility, but forums and containers can`t be assigned to different domains. And Domain Taxonomy module help to solve this.