# What the GPL allows (and requires)

Linux Doctor is **GPL-3.0-or-later** (see [../LICENSE](../LICENSE)). This page
sets out the permissions and obligations that license carries for anyone who
uses, forks, or redistributes it.

## What the GPL grants (permissions)

1. **Use** — run it for any purpose (personal, commercial, any number of
   machines), with no royalty and no permission needed.
2. **Study** — read and understand it; the source is provided.
3. **Modify** — change it however you like.
4. **Share** — redistribute verbatim copies.
5. **Distribute modified versions** — publish your own version/derivative.

These rights are granted to everyone, free of charge, and cannot be revoked as
long as the licensee complies.

## What the GPL requires (only when they *distribute*)

1. **Copyleft** — a distributed derivative must stay under
   GPL-3.0-or-later; no relicensing to something more restrictive.
2. **Source** — provide the complete corresponding source to whoever receives
   the binaries (or a written offer to do so).
3. **Notices** — keep the copyright, licence and "no warranty" notices; state
   significant changes; include the licence text.
4. **No extra restrictions** — no added terms that limit the freedoms (for
   example DRM that prevents exercising them).
5. **Installation Information** (anti-tivoization) — for a "User Product",
   recipients must be able to install modified versions.
6. **Patents** — contributors grant a patent licence; suing over patents
   terminates the licensee's rights.

## What the GPL does NOT grant

- **No brand rights** — the "Linux Doctor" name and logo are *not* licensed. A
  fork must not present itself as the official project; see
  [trademark.md](trademark.md).
- **No warranty / no liability** — provided "as is".
- **No closed-product use without compliance** — embedding it in proprietary
  software requires the [commercial license](../COMMERCIAL-LICENSE.md).
- **No obligation to contribute back** — changes do not have to be sent
  upstream, only offered as source to the fork's own recipients.

## What this means in practice

- Anyone may copy, fork, modify, and even build a paid service around it — **as
  long as** everything they *distribute* stays GPL, ships source, and keeps the
  notices.
- A company that wants it inside a **closed product** must buy the commercial
  license.
- A distributed copy that hides the licence/source, or ships closed, is a **GPL
  violation** and can be enforced (DMCA / legal).