Why

Software management rational
• Open Source software has, at the least, the potential of producing "better" software. The open source debate is to complex to summarize here beyond mentioning a few points.
• Peer review of complex algorythms reduces errors. gnuPort will implement a number of complex financial concepts. User's of this type of software may have significant financial stakes dependent on the reliability of the information provided. Confidence in the that information is valuable, but difficult to achieve with closed software.
• The basic components can be extended to suit a particular implementation, and incorporated back into the larger package, allowing a user to leverage existing work, devlope new implementations that suit there particular requirements, and realize the benefits of peer review and evaluation.

Business rational
• The financial concepts underlying this software are in the public domain. There is not advantage to having proprietary implementations of those concepts beyond the tradintional business reluctance to give away something that costs money to produce. An open implementation of these concepts can provide a standard implementation which reduces cost and risk (see the first point.)
• By using an open source library of financial tools, a user can eliminate the cost and risk of implementing basic functions, and instead focus on implementing tools that differentiate them from their competition. After all, implementing a price/yield calculation adds not value to a system, but using that function to price a new derivative does provide a differentiator for a business.

1. It ensures that the open-source components of the library remain open-source (with the hope that users continue to enhance them)
2. It allows these components to be incorporated in systems that are not open-source.  This is important for vendors who provide proprietary services based on systems that might incorporate these components.