Libpropc++

[Kresimir Sojat <kresimir sojat gmail com>]

I was just playing around on sourgeforge and found the
http://sourceforge.net/projects/glib-bind. Part of this project is
libpropc++ and in its documentation
(http://ex-code.com/propcpp/PR-short.html) says:

Libpropc++ provides a partial reimplementation of libsigc++. Use this
reimplementation if you want to use libpropc++ to write commercial
software because the license of libsigc++ requires any software using
libsigc++ to be open source.

Is this statement true? Becouse i don't use gtkmm/sigc++ to develop
open source software, and on http://gtkmm.org/license.shtml says:

Note that this license does not require you to release the source code
of your own applications or libraries and does not require you to pay
any fees.

I am realy confused now.