This makes me feel all warm and fuzzy inside. thumbs up
I don't think GlusterFS is GoogleFS clone. As far as I know HDFS isn't meant to be a mountable file system. GlusterFS is a near POSIX-compliant FS that can be mounted with FUSE. The FUSE mounts are then exported via NFS or CIFS. At least that is how it was 2 years ago when I tried it. I think NFS is now a native export option of GlusterFS volumes via the NFS Translator. In my mind GlusterFS is more like Isilon than HDFS.
I don't really like the fact that GlusterFS is in user-space. I think Ceph is a more promising project: http://ceph.newdream.net/
As you mentioned the storage volume can be mounted via NFS too.