Buying FAQ

You have some questions related to the sales of our products? Here are the most frequently asked questions.

If you don’t find the answer, do not hesitate to contact us, we’ll reply quickly.

Do I have to buy the program again if I’m just updating?

If you’re updating the software, you have to pay for it again only if the major version number has changed (the first number of the version).


  • updating from 16.2.30 to 17.0.2 must be paid.
  • updating from 4.0.3 to 4.1.0 is free.

How do I get my invoice?

Contact us if you haven’t received it by email or through your Paypal account a few days after your purchase.

I can’t afford to pay for the price set for the program I need, what can I do?

Feel free to make a donation of the amount of your choice instead. Choose the amount according to what you can afford and what you think is right.

What if I want to try the program before buying it?

Just download it for free and come back later to pay it. Please, don’t forget!

I have contributed to a crowdfunding campaign, do I have to buy the software?

It depends. If you contributed to a campaign a long time ago, or if the amount of your contribution was lower than the price of the tool you need, yes, that would make sense to buy it. In all other cases, just download it for free.

I’m supporting Duduf on Patreon, do I have to buy the software?

It depends. If you’ve contributed an amount equivalent to the price of the tool you need, just download it for free. Otherwise, do what you think is right.

Why do you call your tools Free Software if I have to pay for it?

You have to understand the word free as in freedom or in free speech – what we call Libre in French – and not as in free beer. We’ve tried for more than ten years to deliver everything we do for completely free, relying only on voluntarily donations, and that just wasn’t enough for us to continue our work.

So we have to sell the software, but you’re still free to use it as you wish, redistribute it (for free if you wish), modify it, and share your modifications.

We invite you to read this to know more about this interesting subject.

This being said, if you can’t afford to buy one of our tools… Just download it for free!

Do you even have the right to sell a program released under the GNU General Public License?

Yes, the right to sell copies is part of the definition of free software.

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