This is part of a series of reports to the President and Congress developed by the President's Information Technology Advisory Committee (PITAC) on key contemporary issues in information technology. This report defines open source software, explains PITAC's interest in this model, describes the process used to investigate issues in open source software for high end computing, and concludes with findings and recommendations to the President and Congress. The open source development model represents a viable strategy for producing high quality software through a mixture of public, private, and academic partnerships. This approach permits new software to be openly shared, possibly under certain conditions determined by a licensing agreement, and allows users to modify, study, or augment the software's functionality, and then redistribute the modified software under similar licensing restrictions. The report makes three recommendations. First, the Federal government should aggressively encourage the development of open source software for high end computing. Adopting this recommendation will require a technical assessment of the software needs for high end computing as well as an innovative management plan and funding model for supporting this development. Second, a "level playing field" must be created within the government procurement process to facilitate open source development. Third, an analysis of open source licensing agreements is needed, with an ultimate goal of agreeing upon a single common licensing agreement for open software applications. Two appendixes provide a brief description of the multi-agency technical working group on open source software and a list of open source workshop participants. (AEF)