Terms of use and licence

In effect from 21 September 2026

The short version. This is not a substitute for the full terms below, but it is what they add up to:

  • The web editor is free, for any use.
  • The desktop app comes with a 30-day free trial, then needs a subscription. Personal is for non-commercial use; Business is for commercial use.
  • Your diagrams and files are yours. We claim nothing in them and never upload them.
  • If a trial or subscription ends, every file still opens, renders and exports. Nothing is deleted.
  • You can cancel at any time, and keep access until the end of the period you paid for.

1. Who we are

Gnomon is made by Will Percey, trading as Moonlight Software, a sole trader (“we”, “us”). Our address is [address to be added], and you can reach us at [contact email to be added].

These terms cover the Gnomon desktop app, the Gnomon web editor and this website. By installing or using any of them you agree to these terms. If you are agreeing on behalf of an organisation, you confirm you are allowed to, and “you” means that organisation.

2. The web editor

The web editor is free, for personal or commercial use, with no account. It runs in your browser and works on files on your own computer. We may change or withdraw features of the free web editor at any time.

3. The desktop app: trial

The desktop app starts a free trial the first time you open it. The trial lasts 30 days, includes every feature, and needs no payment details. It does not turn into a paid subscription on its own. One trial per person or organisation; please do not reset it.

4. The desktop app: subscriptions

After the trial, using the desktop app needs a subscription. There are two, with identical software:

Commercial use means any use in the course of a business or profession, or for money: work you are paid for, work for an employer or a client, and use by or on behalf of a company, charity or public body. Using Gnomon to learn, or for your own projects that earn nothing, is non-commercial. If you are unsure, it is probably commercial, and you are welcome to ask.

Subscriptions are sold by our reseller, Lemon Squeezy, which is the merchant of record: it takes your payment, charges any tax due, and issues your receipts. Its terms apply to the purchase itself. These terms apply to your use of Gnomon.

A subscription renews each month until you cancel it. You can cancel at any time from the link in your receipt or from Settings → Licence in the app, and you keep access until the end of the period you have already paid for. If we change the price, we will tell you at least 30 days before it applies to your next renewal, so you can cancel first if you wish. Refunds are covered in our refund policy.

5. Your licence to use Gnomon

While your trial or subscription is active, we give you a non-exclusive, non-transferable licence to install and use the desktop app on the number of computers your plan allows, for the use your plan allows. We own the software; you are licensed to use it, not sold it. You may not:

Some parts of Gnomon are open-source software licensed to you under their own terms. For those parts, their licences apply instead of this section. Each one is listed, with its licence, in the third-party notices file (NOTICES.md) installed with the app.

6. When a trial or subscription ends

The desktop app opens to a screen that lets you subscribe, enter a licence key, or open any of your files to view and export. The editing tools are paused. We do not delete, lock or hold back any of your files, and the free web editor continues to work with them.

7. Your work is yours

We claim no ownership of anything you create with Gnomon: diagrams, documents, boards, notes, or the images Gnomon produces from them. Gnomon keeps your files where you put them. The app does not upload them to us, and the web editor does not either.

Keep backups of work that matters. Gnomon does not delete your files, but no software is free of faults, and your own backup is the only protection that does not depend on ours.

8. What the app connects to

To check your licence, the desktop app contacts Lemon Squeezy about once a day, and works for 14 days without a connection between checks. It also checks for updates. With your permission it can send crash reports. What each of these sends is set out in our privacy policy.

Gnomon can work with Claude, through your own Claude Code installation. That connection is between you and Anthropic under your agreement with them, and we are not responsible for what Claude produces.

9. Our responsibility to you

We provide Gnomon with reasonable care and skill. Nothing in these terms limits our liability for death or personal injury caused by our negligence, for fraud, or for anything else the law does not allow us to limit.

If you are a consumer

You have legal rights in relation to digital content that is faulty or not as described, and nothing in these terms affects them. We are responsible for loss or damage you suffer that is a foreseeable result of our breaking these terms or failing to use reasonable care and skill. We are not responsible for business losses: Gnomon's Personal plan is for non-commercial use.

If you are a business

To the extent the law allows, Gnomon is provided as it is, and we are not liable for loss of profit, revenue, business, goodwill or data, or for any indirect or consequential loss. Our total liability to you in any 12-month period is limited to the amount you paid us for Gnomon in that period.

10. Ending this agreement

You can stop using Gnomon at any time. We may suspend or end your licence if you seriously or repeatedly break these terms, for example by sharing a licence key, and will tell you why. If we ever stop offering Gnomon, we will give you reasonable notice and refund any period you have paid for and not received.

11. Changes to these terms

We may update these terms, for example when Gnomon changes or the law does. If a change affects you materially, we will tell you at least 30 days before it applies. The date at the top of this page shows when the current version took effect.

12. Law

These terms are governed by the law of England and Wales, and its courts have jurisdiction. If you are a consumer living in Scotland or Northern Ireland, you can also bring proceedings in your local courts.