Support for custom taxonomy

I have a custom taxonomy created for my posts that some posts get assigned to handle a certain feature we have (I use the custom taxonomy to populate a specific RSS feed). The site owner wants to expire the posts from the RSS feed. I know that I can change post categories with the plugin, but is there some way to force the plugin to see and accommodate additional taxonomies assigned to a post.

In this case, I’m using a custom taxonomies, but say, for example, I wanted to extend the post expirator to change the, or remove, a tag instead of a category. I suppose for a custom taxonomy, the procedure would be the same.

The question is, how to do it?