fastsim is distributed under the PolyForm Noncommercial License 1.0.0. That license permits any noncommercial use — research, teaching, academic work, evaluation, personal and hobby projects — at no cost. Commercial use requires a commercial license. This page explains, in plain language, where that line falls, what a commercial license covers, and what it costs.
To order a license or discuss terms, contact info@pathsim.org.
You need a commercial license if you use fastsim in the course of running a business or delivering a commercial product or service. Two distinct scopes matter, because the license governs them separately (one commercial license covers both):
Using the fastsim engine — the Python package, the Rust crate, the solvers, the JIT, FMU import — to do work for a commercial purpose. Examples:
- running simulations as part of a commercial product, service, or paid consulting;
- embedding the Python/native library in a commercial application or internal tooling at a for-profit company;
- offering fastsim-powered analysis to customers.
This is the heart of the code-generation business model and deserves its own
attention. The C code emitted by Simulation.to_c(...) (and to_fmu(...)) is
"Output" under the PolyForm Noncommercial License. The noncommercial
limitation travels with the generated code — every generated file is stamped
with the notice. So:
- Generating C from a fastsim model and shipping that C (or an FMU, a firmware image, a HIL binary, a library, or any artifact built from it) in a commercial product requires a commercial license, even if the generation was done during noncommercial evaluation.
- The generated code is the deliverable a commercial customer most often wants (an embedded controller, a plant model for a HIL rig, an FMU for a toolchain). Distributing it commercially is exactly what the Output terms govern.
A commercial license lifts the noncommercial limitation on the generated Output so you can compile it into, and distribute it as part of, a commercial product.
Distribution of Output is royalty-free. License fees are for generating and using fastsim — never per shipped unit, device, or end user, and with no runtime fees. Output shipped in your products during the license term stays licensed after the term ends.
- Research, coursework, teaching, and academic publications.
- Personal and hobby projects.
- Evaluating fastsim — including generating and compiling C — to decide whether to adopt it commercially.
- Contributing to fastsim itself.
fastsim is licensed per company, not per seat. One flat annual license covers your entire company — every engineer, every CI runner, every automated or AI-agent-driven workflow. No named users, no license servers, no counting.
| Tier | Price per year | Who it's for |
|---|---|---|
| Startup | $1,500 / €1,250 | Companies with fewer than 25 employees |
| Business | $6,000 / €5,000 | Companies with fewer than 250 employees |
| Enterprise / OEM | contact us | 250+ employees, corporate groups, redistribution |
Every license includes:
- Unlimited use company-wide — all users, machines, CI pipelines, and automated agents of one legal entity.
- Royalty-free Output rights — ship fastsim-generated C code and FMUs in your own products, with the noncommercial notice lifted. Products you shipped during the license term stay licensed after it ends.
- Updates — all releases published during the license term.
- Email support — direct access to the developer, best effort.
The tier is determined by headcount at the start of each annual term. A "company" is a single legal entity; affiliates and subsidiaries need their own license or an enterprise agreement. Redistributing the engine or offering the code generator itself as part of a product or service requires OEM terms.
Integration work beyond email support — custom blocks, solver tuning, embedded/HIL bring-up, Simulink migration — is available separately as consulting.
To order, email info@pathsim.org with your company name and tier; you'll receive an order form and the license terms.
If you need an option with no field-of-use restriction, the pure-Python engine pathsim is available separately under the MIT License. fastsim is a drop-in replacement for pathsim's Python API, so prototyping against pathsim and moving to fastsim (or vice versa) is straightforward. Note that pathsim does not provide the C code generator.
| Activity | Noncommercial license | Commercial license |
|---|---|---|
| Research / teaching / personal use | ✅ | ✅ |
| Evaluating the engine and codegen commercially | ✅ | ✅ |
| Running the engine for a commercial purpose | ❌ | ✅ |
| Shipping generated C / FMUs in a commercial product | ❌ | ✅ |
Contact info@pathsim.org for commercial terms.