For i386.rpm
Download package.
log in as root
Locate package and type rpm -ivh gRpmBuilder-x.x-x.i386.rpm (where the X is fill in the version you downloaded).
And its installed! To run type grpmbuilder or make a link to that.
For src.rpm
Download package.
log in as root
Use rpmbuild --rebuild gRpmBuilder-x.x-x.src.rpm (where the X is fill in the version you downloaded). than go to your RPM directory (/usr/src/redhat/RPMS/i386/ on redhat) and you will have a .i386.rpm version of it.
Follow instrutions above
For tar.gz
Download package.
log in as root.
type gunzip gRpmBuilder-x.x-x.tar.gz (where the x's are replace your version).
Than use tar -xf gRpmBuilder-x.x-x.tar
Go inside the new directory, (usually gRpmBuilder-x.x).
Run ./configure to create makefiles
run make to compile the project
run make install to install the project
Project can be ran by typing grpmbuilder in terminal or making a link to the executable.