To get involved, contact maintainer Brian Cameron
More information about getting involved with other GNOME apps (and many tips that apply to GDM) can be found at http://live.gnome.org/GettingInvolved. For GDM internals refer to the GDM documentation.
DebuggingIn most ways, GDM is a typical GNOME App; you should refer to http://developer.gnome.org/debugging for more information on debugging it.
TranslatingJust as many other GNOME applications, GDM is translated by the GNOME translation team.
Drawing IconsAll icons drawn for GDM should match the GNOME Icon Style Guide
DocumentationIf you want to write documentation for GDM, you should join the GNOME Documentation team.