This module enables to specify relations between terms in more detail. For this, you can create different types of relations, which can be added to related terms. It's based on the taxonomy's term_relation table.
For adding the types to the relations, you have to use the Taxonomy Manager.
Additionally, this module contains a feature to show related content, based on the relation type. (e.g. two terms are related with a so called 'see also' relation, when viewing the node a block with nodes tagged with the related terms can shown)
Concerning D7, there is no need to port this module. Relations between terms can be easily rebuilt by adding a term reference field on the term entity. Each relation type would need a separate field, e.g. field_is_located_in.