Here is a patch that adds a new option to the editor preferences, to control the VC-style behavior of the Home key.
Bluefish and SciTE both have a similar option, so maybe I'm not the only one who thinks "Home" should mean "the beginning of the line" :-)
This is my first attempt at using Glade for anything useful, so hopefully I got it right. The only remaining issues I can see are that changing the setting requires a restart of Geany for the change to take effect, and also I didn't update the docs to reflect the new option.
Regards, - Jeff