Replace the default taxonomy boxes with a custom metabox that uses radio buttons… effectively limiting each post to a single term in that taxonomy.
A plugin options page allows the user can select which taxonomies she’d like to switch to using the custom radio-button style metabox.
Originally based on the the class by Stephen Harris
Support
Support is handled in the WordPress forums. Please note that support is limited and does not cover any custom implementation of the plugin. Before posting a question, read the FAQ and confirm that the problem still exists with a default theme and with all other plugins disabled.
Please report any bugs, errors, warnings, code problems to Github
Screenshots
The settings page where you determine which taxonomies will get radio buttons.
This is what the metabox will look like on the post editor screen.