Complex sentence: Symbolics developed a Genera version, named "Open Genera", that included a virtual machine that enabled executing Genera on DEC Alpha based workstations, plus several Genera extensions and applications that were sold separately (like the Symbolics "S-Graphics" suite).
Split into simpler sentences: Symbolics developed a version of Genera, called Open Genera that included a virtual machine that enables the execution of Genera on DEC Alpha based workstations. Symbolics also developed several extensions and applications for Genera that were sold separately (like the Symbolics "S-Graphics" suite).