You can download and install the OS without any product key. It provides standard Linux functionality and the basic Windows-like interface. However, certain "Professional" tools—such as the specialized WxDesktop configuration screens and system tools—typically expire after a 30-day trial period Professional Edition:
In older versions of Linuxfx, users were often met with a prompt to purchase a Professional Serial Key (typically around $35) to unlock specific features. Google Groups Locked Features: Linuxfx Product Key Free