Sheet · Licences
Open-source licences
Back2STEP is a closed-source app, but it stands on the shoulders of many open-source projects. Thanks to everyone who works on them. The full licence texts are also in the app under “About Back2STEP”.
Included in the app
| Component | Used for | Licence |
|---|---|---|
| Python | runtime | PSF License 2.0 |
| Tcl/Tk | window system | Tcl/Tk License |
| Open CASCADE Technology (OCCT) | CAD kernel, writes STEP | LGPL 2.1 + OCCT exception |
| OCP (cadquery-ocp) | Python bindings for OCCT | Apache 2.0 |
| VTK | bundled with OCP | BSD 3-Clause |
| trimesh | reading and checking meshes | MIT |
| NumPy | numerics | BSD 3-Clause |
| SciPy | numerics | BSD 3-Clause |
| Shapely | 2D geometry | BSD 3-Clause |
| GEOS | bundled with Shapely | LGPL 2.1 |
| Rtree / libspatialindex | spatial search | MIT |
| NetworkX | graphs | BSD 3-Clause |
| Manifold (manifold3d) | solids from meshes | Apache 2.0 |
| Matplotlib | preview images | Matplotlib License (BSD-style) |
| Pillow | images | MIT-CMU |
| CustomTkinter | user interface | MIT |
| tkinterdnd2 / tkdnd | drag and drop | MIT / BSD |
| lxml / libxml2 / libxslt | reading 3MF | BSD 3-Clause / MIT |
| certifi | secure connection for licence check | MPL 2.0 |
| PyInstaller (bootloader) | packages it as a Mac app | GPL 2.0 + bootloader exception |
LGPL components
Open CASCADE Technology and GEOS are licensed under the GNU Lesser General Public License 2.1. They are shipped as separate, replaceable libraries inside the app bundle and are only linked dynamically. You may replace them with your own modified versions.
You can get the source code of exactly the versions used from the projects (OCCT, GEOS) or on request by email to info@back2step.com; this offer is valid for three years from purchase. Licence text: GNU LGPL 2.1.
On this website
| Font | Author | Licence |
|---|---|---|
| Barlow, Barlow Condensed | Jeremy Tribby | SIL Open Font License 1.1 |
| JetBrains Mono | JetBrains | SIL Open Font License 1.1 |
Image credit test cube: “Calibration Cube XYZ” – hectorri, CC BY 4.0.
Last updated: October 2026