The open source software movement has received enormous attention in recent years. It is often characterized as a fundamentally new way to develop software. This paper describes an effort to develop an open source Modelica environment to a large extent based on a formal specification of Modelica, coordinated by PELAB, Department of Computer and Information Science, Linköping University, Sweden. The current version of the system provides an efficient interactive computational environment for most of the expression, algorithm, and function parts of the Modelica language as well as an almost complete static semantics for Modelica 2.0.
The longer-term goal is to provide reasonable simulation execution support, at least for less complex models, also for the equation part of Modelica which is the real essence of the language. People are invited to contribute to this open source project, e.g. to provide implementations of numerical algorithms as Modelica functions, add-on tools to the environment, or contributions to compiler itself. The source code of the tool components of the open source Modelica environment is available under the Gnu Public License, GPL. The library components are available under the same conditions as the standard Modelica library. The system currently runs under Microsoft Windows, Linux, and Sun Sparc Solaris. A benchmark example of running a simplex algorithm shows that the performance of the current system is close to the performance of handwritten C code for the same algorithm.