Osxcart, or OS X Converting And Reading Tool, is a library designed to import file formats used in Mac OS X, NeXTSTEP, and GnuSTEP into GTK+/GLib-based programs easily, using a lightweight interface.
The "s" in Osxcart is silent.
Right now, the Osxcart library includes a module for reading and writing property lists (".plist" files) in XML format, and a module for importing and exporting RTF documents to and from GtkTextBuffers.