We know that
.mpp file extension is a proprietary file format. But, Is there any open source viewer which work with these kind of files?
Project Libre has superseded OpenProj and claims Project 2010 compatibility.
http://www.projectlibre.org/ is the homepage
http://en.wikipedia.org/wiki/OpenProj#Fork_-_ProjectLibre gives some history on how OpenProj forked to give rise to Project Libre.
Try MPP Viewer. It works great.