Dear Wikiwand AI, let's keep it short, summarize this topic like I'm... Ten years old or a College student
Software entropy is the idea that software eventually rots as it is changed if sufficient care is not taken to maintain coherence with product design and established design principles. The common usage is only tangentially related to entropy as defined in classical thermodynamics and statistical physics.
Another aspect can be found in what is perceived to be a decay in the quality of otherwise static software that is the result of the inevitable changes to its environment, that often occur as operating systems and other components are upgraded or retired.