Zen Cart is open-source. As such, the intent is that it is extensible. The core of Zen Cart is intended to support a very diverse range of users; however, it is not intended to suit "everyone's" needs directly. Instead, we endeavour to continually make the code more adaptable and able to be enhanced by way of community-contributed/supported plug-in's that can be added to Zen Cart with minimal difficulty. In this regard, we encourage community contributions.
We recognize that contributions are typically created with the aim of solving one's own individual business challenges, and are not generally written to benefit "everyone". We are also aware that contributions are written with varying degrees of skillsets and comprehension of overall code. Thus, we continue to attempt to make it possible to "plug in" without having to alter core code if possible. Not every situation is perfect, but we keep growing in this area.
It's also important to note that community-supplied contributions are written at a certain point in time and are not always compatible with future or earlier versions of Zen Cart. This is a challenge with any community-supported project. Our new contributions section attempts to help minimize the confusion in this by separating contributions based on the version of Zen Cart for which they were initially written.