SD/FAST open source code
SD/FAST is a symbolic multibody dynamics code developed by Dan Rosenthal, Michael Hollars, and Michael Sherman (Sherm) at Symbolic Dynamics Inc. in the 1990s.
SD/FAST was acquired by PTC (formerly Parametric Technology Corp.) and sold by PTC until 2025. PTC has generously contributed it to open source in 2026, in exchange for Sherm's promise to create the open source organization on GitHub and get the code working again with no need for security keys or paying money! The license is Apache 2.0 which is the most permissive (non-viral) open source license (even better than BSD or MIT in some ways).
Please use the GitHub Discussion feature for questions, or file Issues if you have requests or find problems. Pull requests would be greatly appreciated if you fix problems or want to make updates.
Thanks to @esba1ley for adding Mac support and @DonyDominic for a first crack at CI.
Version 2.0 of open SD/FAST is posted now and still has a lot of ancient cruft. I added a CMakeLists.txt to get the code to build, and successfully built it on Linux and Windows. The old examples and a pdf of the manual are there, unchanged from circa 1998.
Other than removing the security code and a few minor formatting fixups, this is SD/FAST B.2.9 from 1998 which is what PTC has been selling for the last 20+ years.
Please let me know what problems you run into. I think there may be some modernizing needed of the generated code, at least to avoid warnings from modern C compilers.