If you try to build the GIT-version, the build fails with following output:

xfce4_orageclock_plugin-oc_config.o: In function `oc_properties_options':
oc_config.c:(.text+0x47b): undefined reference to `xfce_create_framebox'
xfce4_orageclock_plugin-oc_config.o: In function `oc_properties_dialog':
oc_config.c:(.text+0xe53): undefined reference to `xfce_create_header'
oc_config.c:(.text+0xf18): undefined reference to `xfce_create_framebox'
xfce4_orageclock_plugin-xfce4-orageclock-plugin.o: In function `popup_program':
xfce4-orageclock-plugin.c:(.text+0xbdd): undefined reference to `xfce_exec'

At #xfce they say, porting the app to libxfce4ui and adding $(LIBXFCEGUI4_CFLAGS/LIBS) inside panel-plugin/Makefile.am should solve the problem.

Thanks in advance,