Does the customer have the right to use my developments if the contract is terminated due to missed deadlines, and the prepayment is returned 100%?

Question

Law in IT

I need your hint, the Internet did not help, but the question is urgent.
I represent the side of the performer. A customer appeared for a large project - we signed a contract for the development of a web application, agreed to work 30% 30% 40%, payment after the intermediate results were completed by bank transfer, without an initial prepayment, but only for specifically completed milestones. As a result of the work, the first prepayment (30%) was made, an act of acceptance of the stage of work was concluded, the files were dropped to the customer (JS BE base, layout, styles, adaptive, JS FE scripts - everything related to 30% of the paid work).
Unfortunately, it was not possible to meet the deadlines, as a result of which the customer demanded the return of the entire amount of the prepayment. They returned the money, but after 2 weeks they found on the client's domain a frankly licked our work (we ran the code for compliance - 100% match). Tell me, is it legal on the part of the customer or should we write a statement / claim against him in court? The money was returned in full, the contract was terminated, on what basis does the customer use our developments? How does the proof of code authorship take place in the case of a court?
Thank you!

Answer 1

At least you can run into copyright. And easily.
How does the proof of code authorship take place in the case of a court?
Through an expert
Here you are generally very lucky.
The fact is that in cases of copyright infringement, the problem is the assessment of labor, on the basis of which an assessment of damage is given.
In your case, there is a contract and there are amounts paid (and returned).
Thus, you can get even noticeably more for violation of rights than you would receive under a contract for work.

Answer 2

What is written in the contract?
Maybe there "In case of violation of the deadlines, the Customer has the right to demand a full refund of payment and use the received developments at its discretion. "?
For good
1) There is an act of acceptance. How did you get paid back?
2) Since they voluntarily returned, then there were grounds? Well, why then wave your fists after a fight? You have completed the work, returned the payment for some purpose, and now you are thinking "why?".

Answer 3

> Does the customer have the right to use my developments if the contract is terminated due to missed deadlines, and the prepayment is returned 100%?
> Need your hint, the Internet did not help, but the issue is urgent.
So you came to another Internet and decided to try your luck here?
No, not fartanet here too, until you show the contract and say in which jurisdiction it was concluded.
However, you can include Sherlock Holmes, and say that they have such a right.
The logic behind this is this: if you came to consult on the Internet, and not to the person who drafted it for you, on an “urgent issue” on the merits of your contract, then the contract was not drawn up for you - your counterparty sent it to you, and you only waved it, not bothering to clarify what will happen in case of delay. You yourself described your counterparty as a major customer. If so, then they probably know what they're doing.

Answer 4

I will say this - if the price of the issue does not allow you to hire a competent lawyer ~ 30-100 tr - forget it and sleep well. You can finely spoil the customer by publishing a negative about him.
and if the budget allows - hire a lawyer.

Answer 5

It is unlikely that you will be satisfied with the answer to your question ... whether or not the customer has the right to use your developments ... you are not interested in this, but in another thing - whether it is possible for the customer to prohibit the use of developments and / or receive money from him for use.
But the answer is simple here - you can! (the contract was terminated, the result was not achieved and not transferred)
Difficulties in implementation - you can ban and get money only in court, and here you need to prepare, in mathematical terms, the necessary and sufficient evidence to substantiate your requirements.