ProjectLibre is an alternative software to microsoft office project. It can be downloaded from sourceforge here

http://sourceforge.net/projects/projectlibre/files/ProjectLibre/

in this case we are going to install/wget the RPM installer

wget http://sourceforge.net/projects/projectlibre/files/ProjectLibre/1.5.9/projectlibre-1.5.9-1.rpm/download

install with the simple yum -y command and the installation should look as follows:
yum -y install projectlibre-1.5.9-1.rpm
Loaded plugins: fastestmirror, refresh-packagekit, security
Setting up Install Process
Examining projectlibre-1.5.9-1.rpm: projectlibre-1.5.9-1.noarch
Marking projectlibre-1.5.9-1.rpm to be installed
Loading mirror speeds from cached hostfile
epel/metalink                                            |  13 kB     00:00
* atomic: www6.atomicorp.com
* epel: mirror.steadfast.net
* extras: repos.lax.quadranet.com
* rpmforge: mirror.hmc.edu
adobe-linux-x86_64                                       |  951 B     00:00
atomic                                                   | 3.4 kB     00:00
base                                                     | 3.7 kB     00:00
epel                                                     | 4.4 kB     00:00
epel/primary_db                                          | 6.6 MB     00:21
extras                                                   | 3.4 kB     00:00
rpmforge                                                 | 1.9 kB     00:00
updates                                                  | 3.4 kB     00:00
Resolving Dependencies
--> Running transaction check
--> Package projectlibre.noarch 0:1.5.9-1 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
Package           Arch        Version         Repository                  Size
================================================================================
Installing:
projectlibre      noarch      1.5.9-1         /projectlibre-1.5.9-1       14 M

Transaction Summary
================================================================================
Install       1 Package(s)

Total size: 14 M
Installed size: 14 M
Downloading Packages:
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Installing : projectlibre-1.5.9-1.noarch                                  1/1
Verifying  : projectlibre-1.5.9-1.noarch                                  1/1

Installed:
projectlibre.noarch 0:1.5.9-1

Complete!

now in GNOME it should show up under Applications –> Office –> ProjectLibre

reference: http://blog.zwiegnet.com/linux-server/install-projectlibre-on-centos-6/