I finally found instructions ...

Evidently, the RPM does not work below EL 7, but (supposedly) the 
instructions below work on EL 5 and EL 6.  One does not go through this 
manual process if any of the automagic ones worked.  I will post the 
results.

For anyone familiar with the referenced packages/applications below, 
will this significantly "break" anything?  Obviously, the SELinux matter 
below is a separate issue, in that the suggested change lessens security 
for specific circumstances, but this is not "breaking" anything per se.

http://www.hplipopensource.com/hplip-web/install/manual/distros/centos.html

Manual Build and Install Instructions for CentOS

Important

This process has been tested on Cent OS 5 and Cent OS 6
Step 1: Installation Prerequisite Steps

View the current Release Notes for additional information on this release.

Note

You will need root access to complete many of the steps while installing
HPLIP. If you do not have root access contact your system admin for
assistance.
Step 2: Install Dependency Packages

A. Install the development environment.

Click:

Applications
System Settings
Add/Remove Applications

Click the check mark next to "Development Tools" then click "Update".

Complete the "Package Manager" instructions to install the development
tools.

B. Install the HPLIP dependencies.

su -c "yum -y -d 10 -e 1 install cups cups-devel gcc-c++ ghostscript
libjpeg-devel glibc-headers libtool libusb-devel make python
python-devel PyXML openssl-devel net-snmp-devel policycoreutils-gui PyQt
PyQt-devel dbus-python notify-python sane-backends sane-backends-devel
sane-frontends xsane python-imaging python-imaging-devel"

C. Pre Installation Step(s)

In a terminal run:

su -c "rpm -ev --nodeps libsane-hpaio"
su -c "rpm -ev hplip-gui"
su -c "rpm -ev hplip"
su -c "rpm -ev hpijs"

D. Link the libcrypto library. By default they are not linked as needed
for HPLIP.

su -c "ln -s /lib/libcrypto.so.0.9.8b /lib/libcrypto.so"

Step 3: Disable SELinux

Because the newer version of HPLIP is not part of the SELinux
policy--SELinux needs to be disabled.

Run:

su -c "gedit /etc/selinux/config"

Change the line from "Enforcing" to "Disabled".
Step 4: Download HPLIP

Note

We recommend that you download the HPLIP tarball to your home or desktop
directory.

A. Click here to Download the Regular Tarball

B. Go to the directory where you downloaded the HPLIP tarball.

Example:

cd ~/Desktop

C. Uncompress the tarball.

Enter this command:

tar xvfz hplip-3.15.7.tar.gz

This will create a directory with the same name as the tarball file.

D. Change your working directory to the hplip-3.15.7 directory.

Example:

cd hplip-3.15.7

Step 5: Configure HPLIP for installation

This step configures the development environment and checks that your
system is ready to install HPLIP.

Enter this command (select the appropriate command depending on your
system configuration):

Note

For CentOS 5.x use one of the commands:

32 bit distro users (most users will use this command):

./configure --prefix=/usr --with-hpppddir=/usr/share/cups/model/HP
--enable-qt3 --disable-qt4 --disable-hpcups-install
--disable-cups-drv-install --disable-cups-ppd-install
--enable-hpijs-install --enable-foomatic-drv-install
--enable-foomatic-ppd-install --enable-foomatic-rip-hplip-install
--disable-fax-build --disable-dbus-build --enable-network-build
--enable-scan-build --disable-policykit --enable-libusb01_build
--enable-udev_sysfs_rules --enable-doc-build

64 bit distro users:

./configure --prefix=/usr --with-hpppddir=/usr/share/cups/model/HP
--libdir=/usr/lib64 --enable-qt3 --disable-qt4 --disable-hpcups-install
--disable-cups-drv-install --disable-cups-ppd-install
--enable-hpijs-install --enable-foomatic-drv-install
--enable-foomatic-ppd-install --enable-foomatic-rip-hplip-install
--disable-fax-build --disable-dbus-build --enable-network-build
--enable-scan-build --disable-policykit --enable-libusb01_build
--enable-udev_sysfs_rules --enable-doc-build

Enter this command (select the appropriate command depending on your
system configuration):

Note

For CentOS 6.x use one of the commands:

32 bit distro users (most users will use this command):

./configure --with-hpppddir=/usr/share/cups/model/HP --prefix=/usr
--enable-qt4 --disable-libusb01_build --enable-doc-build
--enable-cups-ppd-install --disable-foomatic-drv-install
--disable-foomatic-ppd-install --disable-hpijs-install
--disable-udev_sysfs_rules --disable-policykit
--disable-cups-drv-install --enable-hpcups-install
--enable-network-build --enable-dbus-build --enable-scan-build
--enable-fax-build

64 bit distro users:

./configure --with-hpppddir=/usr/share/cups/model/HP --libdir=/usr/lib64
--prefix=/usr --enable-qt4 --disable-libusb01_build --enable-doc-build
--enable-cups-ppd-install --disable-foomatic-drv-install
--disable-foomatic-ppd-install --disable-hpijs-install
--disable-udev_sysfs_rules --disable-policykit
--disable-cups-drv-install --enable-hpcups-install
--enable-network-build --enable-dbus-build --enable-scan-build
--enable-fax-build

Step 6: Run Make

This step will compile the HPLIP source.

Important

You want to run make as a regular user, NOT as root.

Enter this command:

make

Step 7: Run Make Install

This step will install HPLIP.

Enter this command:

su -c "make install"

Step 8: Post Installation Step(s)

A. For normal users other than root add user name to "lp" and "sys" group:

su -c "/usr/sbin/usermod -a -G lp,sys $USER"

Restart your PC (or) logout and login

B. If you are going to be setting up a printer with USB and the printer
is already plugged in, you will need to do one of the following:

     Unlpug and re-plug in the USB printer, or
     Restart your PC.

Failure to do this will cause your USB printer to not be detected by HPLIP.
Step 9: Configuring your printer using hp-setup

Continue to hp-setup