It's a plain Free Pascal program, and it uses GTK.
unit frmmain;
interface
uses
gtk,gdk,fpgtk,fpgtkext,pgEditor,frmlink,sysutils,classes,fpdeopts;
Hum, mwouais, maybe, but usually something that uses GTK should be a Lazarus program and not plain pure Free Pascal program.
In a Lazarus application wouldn't find direct uses of units like
gtk or
gdk. Also nothing stops users from writing non-LCL GUI applications that directly interface to the widgetset, be it GTK, Qt, Win32, Cocoa, MUI or whatever.