The Open Unified Process (OpenUP) is a part of the Eclipse Process Framework (EPF), an open source process framework developed within the Eclipse Foundation. Its goals are to make it easy to adopt the core of the RUP / Unified Process.
OpenUP preserves the essential characteristics of RUP / Unified Process, which includes incremental development, use cases and scenarios driving development, risk management, and architecture-centric approach.
The most agile and lightweight form of OpenUP, OpenUP/Basic, targets smaller and co-located teams interested in agile and incremental development. Small projects constitute teams of three to six people and involve three to six months of development effort.