Free or commercial
One checking algorithm: as a simple Windows app or a console tool for developers. The licensing rules are the same.
Free: personal, non-commercial
The app, the command-line tools and the neural networks (models) are free for personal non-commercial use (CC BY-NC 4.0): your own texts, study, hobby, non-commercial research. No registration, no key, no limits.
Commercial licence
For paid work, clients, companies, schools and universities, or products. One licence covers everything together: the app, the command-line tools and the models. You buy the right to use the software commercially, not the models separately and not a subscription service.
command line and models
Prefer the terminal or Python? The same detector runs from the command line — under the same rules as the app.
The linda_pro package and tools (python -m linda_pro) live on GitHub; the models and calibration (about 2.9 GB) live on Hugging Face and the app downloads them for you. Personal non-commercial use is free (CC BY-NC 4.0); commercial use needs the same licence key as the app: the key is your proof of purchase, the tools themselves never ask for it.
What do I need?
Windows 10/11, 64-bit. Loupe: CPU, 4 GB RAM minimum (8 GB preferred), about 0.3 GB models and 2 GB free disk. Assay: 8 GB RAM minimum (16 GB preferred), about 2.9 GB models and 6 GB free disk; DirectX 12 GPU with 8 GB VRAM recommended for FP32, 4 GB unvalidated. CPU fallback is slower. Timings depend on text length, hardware and markup; old FP16 timings are not current FP32 guarantees. See Which version? and Trust.