GTK package purpose in seafile server code

Hi, I am interested to install seafile server in my ubuntu but I could not understand the purpose of GTK package in the autogen script. Kindly let me know the reason why we need the below two lines.
/Seafile/seafile-server$ vi autogen.sh
GETTEXTIZE_URL=“ftp://ftp.gtk.org/pub/gtk/v2.0/glib-2.0.0.tar.gz
else
GETTEXTIZE=“gettextize”
GETTEXTIZE_URL=“ftp://alpha.gnu.org/gnu/gettext-0.10.35.tar.gz