Most of the Windows CE phones of that era (pre-Windows Phone 7) were also basically "rooted" - i.e. you could install any .CAB and there was nothing stopping you. But Linux is a real operating system and Windows CE is basically on the same level as Windows 95 from an architecture standpoint.

A friend of mine worked at a cell phone repair shop and it was fairly common for someone to bring in their bulky keyboard-slideout HTC PDA that had frozen and typically the only recourse was a "hard reset" - reverting the phone to factory settings and removing all stored data (which was in the MB those days). Of course WinMo on most PDAs of the time was quite capable of keeling over all by itself without the aid of third-party programs, so the user couldn't always be blamed.