As the creator of MagpieRSS I know exactly what you're talking about.
And yes, you include it. There are skills demonstrated in a popular open source project which are interesting and relevant, and very very few people are proud of the code they wrote in 2001, no matter who they are or what they do.
You wrote that! I used that when I first started doing web development to show posts from certain categories in wordpress before that feature made it into the core.
I used MagpieRSS in mefeedia.com, thanks for that :) Just think, it may have been dodgy, but my own code would have been much dodgier, so don't feel too bad :)
And yes, you include it. There are skills demonstrated in a popular open source project which are interesting and relevant, and very very few people are proud of the code they wrote in 2001, no matter who they are or what they do.