Overview
OpenUP preserves the essential characteristics of RUP / Unified Process, which include iterative development, use cases and scenarios driving development, risk management, and architecture-centric approach. Most optional parts of RUP have been excluded, and many elements have been merged. The result is a much simpler process that is still true to RUP principles.
OpenUP targets small and collocated teams interested in agile and iterative development. Small projects constitute teams of 3 to 6 people and involve 3 to 6 months of development effort.
Read more about this topic: Open UP/Basic