Can we modify an extension and upload it as our own?

Hi

I want to know if is it Ok to modify a free extension to support the newer version of opencart and upload it to extension directory for free or price?

If yes, can you please tell me what should I care about while doing this? Like giving credit to the author whose extension I modified?

Unless the extension has a license file that specifically allows this, or you're able to contact the author of the extension directly, I would highly recommend you don't do this. If you upload an extension that has code from another extension, and the developer complains about it, you'll be banned from the OpenCart store and forums.

If you plan on releasing a commercial extension, I would strongly encourge you write all your own code. It allows you to understand and have control over all the code in your extension, and gives your customers some assurance that you're a competent developer.

Johnathan wrote:Unless the extension has a license file that specifically allows this, or you're able to contact the author of the extension directly, I would highly recommend you don't do this. If you upload an extension that has code from another extension, and the developer complains about it, you'll be banned from the OpenCart store and forums

Basically all extensions (except templates!) should be licensed under the GNU/GPL.
This license allows you (and force you to) adopt the extension to your needs and if you want you can publish it.
If you find that the extension has bugs, or should be modified with new features, go ahead and publish.

Generally it is recommended to contact the author - before you start, or after you have finished your work.
I know that most of the developers are cooperative - some are very strange.
If he agree, you can use the same name and publish.
If not, use a new name - BUT state that this 'new' extension is a 'derivat' of someone alse work. If you do that not, you will get in troubles.
In every case you have to follow the original license, if it is GPL > GPL, if AGPL > AGPL, etc.
Or 'downgrade' the license - but never change from a GPL to a commercial.

What you never can do, is to rework an existing extension - maybe with the same code - and sell it.
Result will result in a ban of the OC-Store (or whereever you publish it) and possible the laywer.

Another point is if the license is a 'commercial'.
Then you can modify whatever you want, but NEVER PUBLISH, otherwise the laywer could knock on your door ..

A third point is taking or using another idea, and build a completely new extension. New = all lines are written by you and nothing is copied!
In such a case, you can do what you want.
Except .. publishing it in the OC-store.
They like it not very much if another extension will do the same ...

The extension is free and as I told you it is not compatible with OC 2 - I can write the code from the start but don't have much time to do that's why I was asking but I think I would first contact the Author and see what he says, if he refuse I wouldn't use his code and rewrite the whole code. Main problem is to have an extension which do the same as one of the extension already there and the only difference it has is, it is compatible with only OC 2

Can I still upload the extension to OC's extension directory? Wouldn't similar application would be filtered by OC team?

Still, the Problem will always remain, what is a 'default Routine', and what is 'Custom Code'. It is a never ending Story, so, as long as it is free, under GPL/GNU anyway, there is just no way to, legally, prohibit one from using an existing 'Routine' or 'Common Knowledge', to save a little time, by writing a 'new' Mod. Who cannot accept such, should never participate on any Open Source Development, in any form.
My 2 Cent only
Ernie

Scripts under a GNU license can use always existing code.
THE problem / issue is, that too many developers are using existing code (lines) and do not publish from whom these are (the origonal author).
Still OpenCart had this 'problem' a very long time.

If there is already an extension doing something but only for OC2 or only for OC1

Can someone create the same functionality's extension for the version which the other version doesn't support and upload to the OC's Extension Directory? Ofcourse, the code would be written from the ground by new author.

What is OpenCart's policy in this case?

Yes, as long as the code is all your own, you can upload it to opencart.com. Lots of people have copied my (and other developers') extension design / layout / ideas, and Daniel allows them to sell their own versions.

(Personally, I think it's pretty unprofessional to copy someone else's extension and take part of their sales, but there are lots of people out there who don't seem to have the same ethical view. It seems like everyone would benefit a lot more if people would come up with unique extensions, since there would then be more variety.)

Not that that applies in your case, since the author of the original isn't selling it.

Thanks Johnathan, main purpose is to provide an extension which is not available in OC2 not to copy an existing extension