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+# CRDOP license and usage rights
+
+**CRDOP** (MAX25-SoftModem) is **free software** under the **GNU General Public License version 3** (GPL-3.0-or-later).
+
+License files:
+
+| File | Scope |
+|------|-------|
+| [stacks/crdop/LICENSE](../LICENSE) | CRDOP subproject |
+| [LICENSE](../../../LICENSE) | MainAX25-Stack repository root |
+
+---
+
+## Summary (not legal advice)
+
+GPLv3 grants everyone — **private individuals and commercial entities** — the right to:
+
+| Right | Meaning |
+|-------|---------|
+| **Use** | Run CRDOP for any purpose (personal, club, business, government) |
+| **Study** | Read and learn from source code |
+| **Modify** | Change code to suit your needs |
+| **Distribute** | Share originals or modified versions |
+| **Commercial use** | Sell services, products, or support built on CRDOP |
+
+**Copyleft obligation:** When you **distribute** CRDOP (or a combined work based on it), you must:
+
+1. Provide **corresponding source** (or a written offer valid ≥ 3 years).
+2. License derivatives under **GPLv3** (or later, per "or later" clause).
+3. Preserve copyright notices and license text.
+4. Document changes if you modify files.
+5. Pass through patent retaliation and anti-tivoization terms as GPLv3 requires.
+
+**No warranty:** Software is provided **AS IS** — no implied fitness for a particular purpose.
+
+---
+
+## Private use
+
+| Scenario | Obligation |
+|----------|------------|
+| Run CRDOP on your own computer | None beyond GPLv3 acceptance |
+| Modify for personal use only | No distribution → no source-offer obligation |
+| Internal company use (no binary redistribution) | Same as private — no copyleft trigger until you distribute |
+
+---
+
+## Commercial use
+
+| Scenario | Obligation |
+|----------|------------|
+| Sell pre-built PCs with CRDOP installed | Provide source (or written offer) to recipients |
+| Ship hardware interface **with** CRDOP binaries | GPL applies to distributed software; hardware schematics you create separately may use another license if they are not a derivative of the GPL code |
+| SaaS / hosted service (no binary to users) | AGPL would impose network copyleft — **CRDOP is GPL, not AGPL**; consult counsel for your deployment model |
+| OEM integration in a product | Ensure GPL compliance for all distributed GPL components; document how users obtain source |
+
+**Practical path:** Include `LICENSE`, offer source at your support URL or ship `stacks/crdop/` tree, and state "based on CRDOP (GPLv3)".
+
+---
+
+## Combined works (MAX25-Stack)
+
+MAX25-Stack bundles CRDOP with daemon, terminal, and plugins. Distribution of the **combined stack** triggers GPLv3 obligations for the GPL-licensed portions. Other components may carry their own licenses — check root `LICENSE` and per-directory notices.
+
+| Component | Typical license |
+|-----------|-----------------|
+| `stacks/crdop/` | GPL-3.0-or-later |
+| MAX25 daemon / terminal | GPL-3.0-or-later (repository default) |
+
+---
+
+## What you may not do
+
+| Restriction | Reason |
+|-------------|--------|
+| Relicense CRDOP under proprietary terms | GPLv3 copyleft |
+| Remove copyright / license notices | GPLv3 §4 |
+| Imply warranty or liability from authors | GPLv3 §15–16 |
+| Distribute without source (when distributing binaries) | GPLv3 §6 |
+
+Patent suits against GPL users can terminate your license (GPLv3 §8).
+
+---
+
+## ARDOP-plugin (separate)
+
+**ARDOP-plugin** is an optional MAX25-Stack registry entry — **not** part of the CRDOP GPLv3 tree.
+
+| Item | Policy |
+|------|--------|
+| CRDOP coupling | **None** — third-party ARDOP host software |
+| Registry | [plugins/external/ardop/README.md](../../../plugins/external/ardop/README.md) |
+
+CRDOP GPLv3 obligations apply to **CRDOP code**, not to operator ARDOP host software.
+
+---
+
+## Contributor grants
+
+By contributing to `stacks/crdop/`, you agree that contributions are licensed under **GPL-3.0-or-later**, consistent with the repository [CONTRIBUTING.md](../../../CONTRIBUTING.md).
+
+---
+
+## Full license text
+
+- Online: <https://www.gnu.org/licenses/gpl-3.0.html>
+- In tree: [stacks/crdop/LICENSE](../LICENSE) · [LICENSE](../../../LICENSE)
+
+---
+
+## Related
+
+| Doc | Topic |
+|-----|--------|
+| [docs/CRDOP.md](../../../docs/CRDOP.md) | Project rule §5 License |
+| [INDEX.md](INDEX.md) | Documentation index |