Lazarus Code

Abstract

I’ve been asked to look into the possibility of taking a 15-year-old piece of open-source software and updating it to work on a current system used by my company. The code itself doesn’t seem to be too bad, at least no worse than the code I’m used to reading, but I suspect it might be easier to write a new version from scratch than to try to understand code that I didn’t write and which no one has actively maintained for several years. What is the point at which I should decide to ignore this old code and write something new?