The main purpose of the digital certificate is to ensure that the application belongs to the entity to which the certificate was issued. The Software Developer digital certificate does not guarantee that a signed application is safe to run, but rather informs the user that the software was digitally signed by Software Developer and verified by a trusted Certificate Authority (CA).
GLib is a cross-platform software utility library that began as part of the GTK+ project. However, before releasing version 2 of GTK+, the project's developers decided to separate non-GUI-specific code from the GTK+ platform, thus creating GLib as a separate product. GLib was released as a separate library so other developers, those who did not make use of the GUI-related portions of GTK+, could make use of the non-GUI portions of the library without the overhead of depending on the entire GUI library. developer.gnome.org
About (from Software Developer at developer.gnome.org)
“library.gnome.org aims to be the central place for documentation related to the GNOME project, be it for users, system administrators or developers. Its development tree is hosted in the GNOME GIT repository, in the library-web module.”