I’ve been that CS undergrad in the past who aided another department’s research, and the quality of my work back then was every bit as bad as you might expect. Of course I, like many of my CS peers, arrogantly thought I was doing great work at the time...

For sure, talented undergrad CS developers exist, but in my experience there are far fewer of them than many people might think. Experience counts for a lot, especially when trying to deliver even average quality software work.

As for something made by undergrads that is “maintainable” to a standard broadly comparable with an experienced developer? Maybe if you get lucky...