The custom author byline plugin has a filter on line 32. It says:
add_filter( 'author_link', 'custom_author_uri' );
but it doesn't seem to work. My theme calls for an author name to show the link, but it doesn't appear using the custom value.
I tried changing it to match something I saw on the codex to say instead:
... but that didn't work either.
I did manage to find a workaround though. By editing my theme, instead of the plugin, I can include this:
<a href="<?php echo get_post_meta($post->ID, 'uri', true); ?>" rel="author"><?php the_author(); ?></a>
and now I get the intended results. the author's name is shown, via the custom field, along with a link to the custom author URI.
I thought I would share this in case anybody knows how to fix the plugin, or in case anybody wants to try my workaround.