I don't think changed it because they like an online version better. It's a step to invite more contributors to it, as the offline version did not get maintained sufficiently (it was horribly out-of-date and incomplete).
Posted Apr 30, 2012 20:05 UTC (Mon) by jengelh (subscriber, #33263)
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xfce thankfully belongs to the program pool that you do not need a manual for, if you had prior encounters with the "plain desktop and a taskbar" DE concept.