Who Owns a Derivative Work of Copyrighted Software

I had a handshake agreement with someone who produced copyright software for the USA. I am in Canada and made changes to the copyright work with permission, but not written. The original founder handed over everything to his kid, who now wants to claim ownership of our derivative work. We will cease use of the original copyright work, be does he have a case on the code/software we developed?

he owns what he wrote, you own what you wrote, because yours is a derivative work,you cannot use what you wrote without a license from him, which you had under your agreement; the hard part will be proving it in court.

Thanks for response. For clarity, which part do you think will be hard to prove in court?

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Quoting korazy

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Thanks for response. For clarity, which part do you think will be hard to prove in court?

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Where was the producer of the original software; Canada or US? Producing software FOR the us is not the same as producing software IN the US. If in the US, there is an inherent right in the works. If it was produced in Canada, Canadian law would apply and I don't know diddly about Canadian copyright law.

Had he registered his copyrights with the US copyright office?
Have you registered your copyrights with the US copyright office?

Where is the new owner of the original software; Canada or US?

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Quoting jk

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Where was the producer of the original software; Canada or US? Producing software FOR the us is not the same as producing software IN the US. If in the US, there is an inherent right in the works. If it was produced in Canada, Canadian law would apply and I don't know diddly about Canadian copyright law.

Had he registered his copyrights with the US copyright office?
Have you registered your copyrights with the US copyright office?

Where is the new owner of the original software; Canada or US?

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Original owner is in the US.
I am in Canada
Original work produced in the US.
Derivative work produced in Canada.
New owner recently registered copyright in US.
Original owner did not register copyright.
I have not registered any copyright.

did the new owner register your derivative work too either within the copyright of the main work or as a derivative work?


the issues I see:

you need to be able to prove you created the derivative work


if you intend on using the original, you need to prove your licence allows you to do so.

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Quoting jk

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did the new owner register your derivative work too either within the copyright of the main work or as a derivative work?


the issues I see:

you need to be able to prove you created the derivative work


if you intend on using the original, you need to prove your licence allows you to do so.

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No, owner did not register the derivative work.
We do not intend to continue to use the original, moving forward, we are stopping. My question is can they claim ownership of the changes we made.

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Quoting korazy

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My question is can they claim ownership of the changes we made.

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can you prove you created it or that the original creator of the primary work didn't?

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Quoting jk

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can you prove you created it or that the original creator of the primary work didn't?

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Only I have the source code for our work, they do not. What kind of evidence would be sufficient?

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Quoting korazy

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Only I have the source code for our work, they do not. What kind of evidence would be sufficient?

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with software i honestly couldn't say. i dont do software so i couldnt really say how or what would prove you created it.