Comment 28 for bug 262617

Correction:
Not all applications called with 'open' seem to handle the URL-encoded spaced well (I was wrong e.g. about Preview.app).

Further tests on Mac OS X 10.5.8 Leopard (i386):

a) Inkscape built and run as unix-style command line app
works fine with 'Gimp on OS X' 2.6.11 newly installed and started out-of-the-box with new preferences.

b) Inkscape built, packaged and run as osxapp:
Applications like Pixen, Paintbrush or Preview launch the same way as with the command line version (called with "open -a {app-name}"). However, there are interferences in the shell environment inherited by the spawned process from Inkscape which cause interaction with e.g. 'Gimp on OS X' to fail (because the two application use too different packaging strategies and not fully compatible bundled library versions), as well as with MyPaint (pyGtk) and possible other GTK+ applications.

If a wrapper script for the external application unsets these environment variables (set by the inner launcher script of Inkscape.app), the external editor works also with the osx-packaged Inkscape version:

#unset PYTHONHOME
unset PYTHONPATH
unset DYLD_LIBRARY_PATH
unset FONTCONFIG_PATH
unset PANGO_RC_FILE
unset GTK_IM_MODULE_FILE
unset GDK_PIXBUF_MODULE_FILE
unset GTK_DATA_PREFIX
unset GTK_EXE_PREFIX
unset GNOME_VFS_MODULE_CONFIG_PATH
unset GNOME_VFS_MODULE_PATH
unset XDG_DATA_DIRS
unset ASPELL_CONF

Not sure how this could be addressed - maybe better discussed in a separate report.