The help function is broken with Xfce 4.10 since it relies on xfhelp4 from xfce-utils which has been removed from Xfce 4.10.
Created attachment 4869 Display help page In FreeBSD we use this patch, it displays man page.
This was fixed with http://git.xfce.org/apps/xfce4-screenshooter/commit/?id=5aaa5c3c5fbb9cae8636007a832b547f7b9178ba (2013-07-13)
Created attachment 5460 Proper patch using Xfce's built-in doc launcher I've put the actual fix that uses libxfce4util properly in bug 10197 (https://bugzilla.xfce.org/show_bug.cgi?id=10197).
Newest patch applied in commit bbc5f465bbb3743bdc755b4add311281055c9158. Marking as resolved.