GNUstep Renaissance is a portable GUI interface for GNUstep and Cocoa, contrast to Gorm, which is not portable to Cocoa. It uses XML format rather than binary format in Gorm. And it uses relative position rather than absolute position in Gorm. Programmers can choose the one they prefer for the GUI interface. GNUstep supports Gorm interface by default. You have to install Resaissance in order to use it. You can get it from its homepage, or get the lastest source code from GNUstep CVS in dev-libs/Renaissance/.
Renaissance comes with good document. There is also a tutorial of GNUstep Resaissance.