Lots of folks using WordPress sites with multiple authors may run into this problem. You want to attribute correct credit to the writer/author of the article, but not give out access to your WordPress install. Maybe because it's a one-time article, maybe not, who cares?
If the author of your blog entry is different than your logged in user and you don't want to have to create a separate user account, just add the name as you'd like it to appear to the Custom Author Byline panel below the post editor. Easy!
For more information on the WordPress
Custom Author Byline plugin and how to use it, visit the information page at the preceding link.
1.1
Renamed function(s) to eliminate conflict with some other plugins.
1.0
Brand new release. Props to @ron_r for giving me a hand with a filter/function.