Has anyone installed the open source version?
There is no open source version of VMWare Fusion.
It's the open source packages used in VMware Fusion, not the VMware Fusion.app itself.
As an example the VMware-fusion-open-source-502.tgz file contains the following packages:
at-spi-1.22.1.tgz gtk-engines-2.18.4.tgz
atk-1.22.0.tgz gtkmm-2.12.7.tgz
atk-1.30.0.tgz gtkmm-2.20.1.tgz
busybox-1.11.1.tgz iconv-1.9.2.tgz
cairo-1.6.4.tgz jansson-2.3.tgz
cairo-1.8.8.tgz libart_lgpl-2.3.17.tgz
cairomm-1.6.0.tgz libbonobo-2.22.0.tgz
cairomm-1.8.2.tgz libfuse-2.5.3.tgz
cpio-2.9.tgz libgksu-2.0.11-1.tgz
dosfstools-2.11.tgz libglade-2.6.0.tgz
e2fsprogs-1.39.tgz libgnomecanvas-2.14.0.tgz
e2fsprogs-1.40.11.tgz libgnomecanvasmm-2.16.0.tgz
gail-1.22.3.tgz libgtop-2.14.9.tgz
gawk-3.1.5.tgz libiconv-1.9.2.tgz
gcc-3.3.3.tgz libmspack-0.0.20040308alpha.tgz
gcc-4.1.2-4.tgz librsvg-2.16.0.tgz
gcc-4.1.2-7.tgz libsigc++-2.0.17-1.tgz
gettext-0.14.6.tgz libsigc++-2.2.9.tgz
gettext-0.17-1.tgz log4cpp-1.0.tgz
gettext-0.17.tgz ntfs-3g-1.516-1.tgz
gksu-2.0.0.tgz ntfsprogs-2.0.0_802226.tgz
glib-2.22.1-1.tgz ocaml-3.12.1.tgz
glib-2.22.4-1.tgz pango-1.20.5.tgz
glib-2.24.0.tgz pango-1.26.0.tgz
glibmm-2.16.4.tgz pangomm-2.26.0.tgz
glibmm-2.22.1-1.tgz procps-3.2.7-1.tgz
glibmm-2.22.1-3.tgz reiserfsprogs-3.6.19.tgz
glibmm-2.22.1.tgz sed-4.1.5.tgz
glibmm-2.24.0.tgz startup-notification-0.9.tgz
gnome-menus-2.30.2_802226.tgz tar-1.20.tgz
grub-0.97.tgz udev-135.tgz
gtk+-2.12.11.tgz util-linux-2.13_pre7.tgz
gtk+-2.20.0.tgz