BcalcOS uses Xfce as its desktop environment.
Xfce is a lightweight desktop environment for Unix-like operating systems. It is designed to be fast and relatively light on system resources while still providing the features users expect from a modern graphical desktop.
Why Xfce?
Xfce fits well with the overall approach of BcalcOS.
BcalcOS is intended to provide a complete desktop without being unnecessarily complicated or resource-intensive. Xfce provides a familiar graphical environment while giving users considerable control over how their desktop looks and behaves.
It is also modular. Rather than being one large application, Xfce is made up of separate components that work together, including the window manager, panel, desktop manager, session manager, settings manager, file manager, and application finder.
A Traditional Desktop
Xfce provides the sort of desktop environment many Linux users will already recognize.
There is a panel, application menu, desktop, file manager, windows, workspaces, settings, and the usual collection of desktop utilities. These components can be customized without requiring users to completely change how they interact with their computer.
Xfce and XLibre
BcalcOS uses Xfce together with XLibre as its X11 display server.
Xfce continues to support X11.
What Does This Mean for Users?
For most users, it simply means that Xfce is the desktop you see when you log in to BcalcOS.
You can use it as provided or customize it to suit your preferences.
The Short Version
BcalcOS uses Xfce because it provides a mature, familiar, lightweight, and configurable desktop environment.