We don’t even specify linking glibcxx_3.4.11, so gcc must automatically link it behind the scenes. There’s probably a compiler switch that would tell it to static link it. I’m not sure what the licensing issues would be. Typically, compiler stuff is fully redistributable.
It is because the system the lead developer is using is probably “bleeding edge” (as in very new, very recent, very uptodate). This is not a system that should be used to build something aimed to be redistributable to the widest audience.
Please see some potential improvements in my thread http://bitcointalk.org/index.php?topic=612.0
Do the Windows and MacOS binary downloads come without these respective libraries (re boost/wxWidgets) ? The Linux specific parts such as glibc and GCC toolchain to use the LGPL for the runtime redistributable components. I believe the X11 library parts to be MIT. I believe the GTK+ to be LGPL. Freetype is LGPL (and/or BSD like). Expat is LGPL. OpenSSL is BSD+Notice (although you already know that from your credits).
Looking through the list “ldd bin/{32,64}/bitcoin” I think I have just about covered them all.