Hey, Is it legal to modify open source project and change it without permission of author? Or can project be changed without credits to author ? Or does it depends on project and its terms ? Thanks
Generally speaking, the reason why it is open-source is that it allows you to make modification to the source codes without seeking explicit permission from the author. However, for the most parts, you are not allowed to remove any credits to the authors. As to what you can or cannot do depends a lot on the terms being used. Although it is open-source, you will need to still respect the intellectual property and effort from those who works on it.
It is always legal to modify it; that's the main point of open source. If it is for your own private/internal use, that's the end of the story. Change it, use it, no problem. No need to get anyone's permission. If you will be selling the code or a product containing the code (software, or hardware with it embedded), then you may have further obligations depending on the particular license the code came under. As long as you follow those obligations then you don't need to seek explicit permission.
Sure, if it's under the GPL license. But there are other open-source licenses — Apache, BSD, etc. Each comes with its own set of rules.
I didn't get that when I read the OP's questions but you may be right, ziya may have been talking about a different open source licensing.
If you plan to modify open source and planning to sell it, you have to pass on the same open source license on the fully developed software. Further you are not allowed to remove any of the credits in the open source. You have to acknowledge everyones hardwork and credits.
Read the licence. Many opensource projects, are relased throught GPL licence, which allows editing the source code.