Some of the developers are really fond of out-of-tree builds, while others aren't. Basically the idea is to perform the build in a separate directory so that the output from the build process doesn't clutter up the source tree.
This can be done by executing configure from a separate directory. For example:
# tar xzf pvfs2-0.0.2.tgz # mkdir BUILD-pvfs2 # cd BUILD-pvfs2 # ../pvfs2/configure