Gusset licence agreement

Last updated 6 October 2026

This agreement is between you and Fabr Engineering Ltd, a company registered in England and Wales (company number 08826947), whose registered office is at Spelders Hill House, Brook, Ashford, Kent, England, TN25 5PB (“we”, “us”). It sets out what you may do with the Gusset program (“Gusset”). By installing or using Gusset you agree to it. If you use Gusset for a business, you confirm that you may agree to it for that business, and “you” means the business too.

1. Two licences

Gusset is licensed, not sold. Which licence you have depends on your account.

Hobby (free). You may use Gusset for learning, study, teaching yourself, and your own projects that nobody pays you for. You may not use it for work done for an employer, a client or a business, for anything you sell or are paid for, or to produce results that others will rely on commercially. Reports, pictures and animations made under a Hobby licence are marked as such, and you must not remove or hide the mark.

Pro (paid subscription). While your subscription runs you may use Gusset for any lawful purpose, including commercial work, and what you export carries no mark. A Pro licence is for one named person. A business needs one for each person who uses Gusset.

2. What you may do

• Install Gusset on up to two computers that you yourself use, signed in to your own account.
• Keep, share and publish the studies, results and reports you make. They are yours.

3. What you must not do

• Share your account, or let anyone else use your licence.
• Sell, rent, lend or sub-license Gusset, or offer it to others as a service.
• Get round the sign-in, the licence check or the Hobby mark, or help anyone else to.
• Copy, change, decompile or reverse engineer Gusset, except where the law gives you that right and it cannot be taken away by agreement, and except as section 8 allows for the open-source parts.
• Remove copyright or licence notices.

4. Your account and the licence check

Gusset needs you to sign in to an account. It checks your licence with our server when you sign in and every so often afterwards, and runs for up to 14 days without a connection. If it cannot renew the licence in that time it will ask you to connect before it solves again. What the check sends, and what we keep, is set out in the privacy notice. Your models, loads and results are never sent to us.

5. Paying for Pro

Pro is sold through Paddle.com, which is the merchant of record: your order is placed with Paddle, Paddle takes the payment and sends the invoice, and Paddle's terms apply to the purchase alongside this agreement. The subscription runs for a year and renews each year at the price then current until you cancel. We will tell you at least 30 days before a renewal if the price is going to change. You can cancel at any time from your account page; Pro then runs to the end of the year you have paid for and your account becomes Hobby. If you ask within 14 days of first buying Pro, we will refund you in full. The terms say more.

6. Updates and changes

We may update Gusset, and updates may add, change or remove features. While you subscribe to Pro you are entitled to every update we release. We may change what the Hobby licence includes, or withdraw it, on 30 days' notice by e-mail or in the program; a copy you have already installed keeps working under this agreement until its licence next needs renewing.

7. Using Gusset for engineering

This section matters. Please read it.

• Gusset is a calculation aid for people competent to judge its results. It does not replace engineering judgement, and it is not certified to any design code or standard.
• Its results are approximations. They depend on the model, materials, supports, loads and settings you choose, and on assumptions built into the method: linear elastic material, small deflections, static loading, and idealised welds, bolts and supports. It does not predict yielding, fatigue, fracture, vibration, impact, creep, corrosion or the effects of temperature.
• You are responsible for checking that a result is right for your purpose, including by independent calculation or test where the consequences warrant it.
• Do not rely on Gusset alone for anything whose failure could cause death, injury, or serious damage to property or the environment. Such work must be verified independently by a suitably qualified engineer.

8. Other people's software

Gusset includes software written by others, under their own licences, including Qt and PySide6 (LGPL), OpenCASCADE (LGPL), VTK (BSD), Intel oneMKL, NumPy, SciPy and Numba. The full list and the licence texts are in the file THIRD-PARTY-NOTICES.txt installed with Gusset and under Help > About. Those licences, not this agreement, govern those parts, and nothing here limits the rights they give you, including the right under the LGPL to modify and replace the LGPL libraries and to reverse engineer Gusset as far as needed to debug such changes.

9. What we promise

Pro. We will supply Gusset with reasonable care and skill, and it will do in substance what its documentation says. If it does not, tell us: we will put it right within a reasonable time or, if we cannot, refund what you paid for the period affected.

Hobby. The Hobby licence is free, and Gusset is provided under it as it is.

If you are a consumer you have legal rights about digital content that is faulty or not as described. Nothing in this agreement affects them. Beyond what is said here and what the law requires, we make no other promises about Gusset, and in particular we do not promise that it is free of errors or fit for any particular purpose of yours.

10. Our liability

Nothing in this agreement 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.

Subject to that:

• we are not liable for loss of profit, revenue, business, contracts, goodwill or data, for the cost of redesign, rework, repair or recall, or for any indirect or consequential loss; and
• our total liability to you arising from Gusset or this agreement, whatever the cause, is limited to the greater of the amount you paid for Gusset in the 12 months before the claim arose and £100.

You accept that these limits are reasonable given the price of Gusset, that it is a calculation aid whose results you must check (section 7), and that you are better placed than we are to judge and insure the consequences of the designs you use it for.

11. Ending this agreement

You may stop using Gusset at any time and delete your account from your account page. We may end your licence if you break this agreement and, where the breach can be put right, you have not done so within 14 days of our asking. When the licence ends you must stop using Gusset and uninstall it. Sections 7, 9, 10 and 12 carry on.

12. General

We may change this agreement for good reason, for example because the law or Gusset changes. We will tell you by e-mail or in the program at least 30 days before a change that matters takes effect; if you do not accept it you may cancel and, for Pro, be refunded for the unused part of your year. We may transfer our rights and duties under this agreement to another organisation that takes Gusset on; your rights are not affected. You may not transfer yours. If a court finds part of this agreement invalid, the rest stands. This agreement is governed by the law of England and Wales, and the courts of England and Wales have jurisdiction, except that a consumer living in Scotland or Northern Ireland may also bring a claim there.

13. Contact

Fabr Engineering Ltd, Spelders Hill House, Brook, Ashford, Kent, England, TN25 5PB. E-mail: our support address.