The latest stable release is 1.8.0. You can get it on SourceForge.

Simon Haegler kindly contributed a gentoo ebuild for the 1.8 release (please see the ticket for some variations on the ebuild).

• create an opensg directory in your local portage overlay: mkdir -p /usr/local/portage/media-gfx/opensg
• copy the attached ebuild into this dir
• create the digest: ebuild opensg-1.8_rc20070621.ebuild digest (this will download the sources and create additional portage files)
• emerge opensg

David Morris kindly contributed packages for Ubuntu, they are available via launchpad, by adding the following lines to /etc/apt/sources.list:

For Ubuntu Feisty Fawn:

deb     http://ppa.launchpad.net/opensg/ubuntu feisty main restricted universe multiverse
deb-src http://ppa.launchpad.net/opensg/ubuntu feisty main restricted universe multiverse

For Ubuntu Gutsy Gibbon:

deb     http://ppa.launchpad.net/opensg/ubuntu gutsy main restricted universe multiverse
deb-src http://ppa.launchpad.net/opensg/ubuntu gutsy main restricted universe multiverse

The packages required are:

• libopensg-core1 - Base and System libraries for users
• libopensg-core-dev - Base and System libraries for developers

• libopensg-qt1 - WindowQT libraries for users
• libopensg-qt-dev - WindowQT libraries for developers

• libopensg-windowx1 - WindowX libraries for users
• libopensg-windowx-dev - WindowX libraries for developers

• libopensg-glut1 - WindowGLUT libraries for users
• libopensg-glut-dev - WindowGLUT libraries for developers

• opensg-tools - fcdEdit and actorEdit
• libopensg-doc - User and developer docs

A launchpad opensg team for feedback on the packages is also available here.