Siemens Removes OpenRadioss Repository; Community Fork Launches as OpenCourant

Siemens took down the OpenRadioss repository early this month without transitioning it to a read-only archive state, a departure from standard practice when discontinuing open-source projects. The GitHub page remains visible, but the underlying code has been removed entirely, redirecting users instead to information about Simcenter Radioss.

OpenRadioss was the open-source version of Radioss, a finite element solver originally developed by Altair Engineering for crash testing, blast response, impact analysis, and structural loading simulations. Altair released it in September 2022, attracting a diverse international community of researchers, developers, and industry specialists who contributed extensions and improvements to the codebase.

Siemens acquired Altair the following year and maintained the repository publicly for over a year before the abrupt removal. The sudden deletion, without advance notice to the community, raised questions about the company's intentions regarding the project's future.

A fork appears

Brian Clemens, co-founder of Rocky Linux, has already established a fork of OpenRadioss that retains the complete commit history, maintains the original GNU AGPLv3 license, and is available on GitHub. The fork is called OpenCourant, named after mathematician Richard Courant and the Courant-Friedrichs-Lewy (CFL) condition, a fundamental stability criterion used in solvers of this type.

The AGPLv3 license made this fork legally possible. Although Siemens had the right to remove its repository, the license granted anyone the freedom to fork, distribute, and build upon the code. OpenCourant is being developed as an independent community project and is actively seeking contributions from former OpenRadioss developers.

What's already shipping?

The original upstream build pipeline relied on proprietary Siemens infrastructure that could not be transferred to the fork. The OpenCourant team rebuilt this pipeline from scratch, with results that appear solid. Within days of launch, the project is already providing compiled packages for Linux and Windows x86_64 systems.

A closed-source binary called hm_reader, which served as an input reader and was never part of the git history, disappeared when Siemens removed the repository. An unnamed community member who had preserved a copy came forward, the OpenCourant team verified its authenticity, and it is now included in all builds. The team continues to seek specific release archives to enable ARM64 support and expand platform compatibility.

OpenCourant distributions include Starter and Engine packages available in single and double precision, SMP builds, and tools for converting animation files and time history data. Downloads are available from the official downloads page. The INSTALL.md documentation currently reflects the original OpenRadioss version, as the OpenCourant team has not yet updated it for the new project.