On my machine while developing I'm using icons from other application (in particular MS Paint and Paint.NET) as sign for the user that if he chooses to open that file (with our own internal command) it would open in those applications.
Is it legal to extract the icons from those applications and use them? Commit them to repository and then use on all developers' machines (even those that do not have Paint.NET installed)?
Let me make it clear once more. I'm not talking about including those icons in release version. Providing proper icons is up to graphics/skin designer. I'm talking just about the developing process.
Would extracting the icons in run-time either directly or based on file types change anything?
Recently there was a similar question: Can I legally use the icon of a different software? Yet mine differs in that I do not want to release those icons along my application.
EDIT
Let me emphasis an issue which (judging by answers so far) was missed.
If using the icons in above described circumstances was against the license/law (again judging from answers) then how about asking operating system for an icon of the application or an icon associated with the file. This will likely end in showing the very same icon…
How about file browsing apps for which showing those icons is crucial part of their working rather than a nice but minor feature?
How (from license/law point of view) is operating system/file browser/… different from my own developed application that they are (as I assume they are) allowed to query those icons and show them while I'm not. After all one could claim that looking at his beautiful icons in file browser aided my development like unit tests do and so I should pay extra like I do for using those unit tests…
(Also if icon would be queried at run-time from operating system it might be irrelevant whether it is on my development machine or on a released version at client machine…)
Best Answer
Technically speaking, the moment you copy the icon, you have to abide by the licensing terms, or otherwise obtain the copyright holder's permission. So even using them in your own development efforts without ever including them in a distribution could be considered copyright infringement and punishable as such - although the chances of you getting sued over it are probably quite small.
There's an easy practical solution: Use placeholder artwork under a permissive license. Creative Commons is chock-full of icons that are good enough for this purpose, and without any legal obstacles for you - many of them can even be re-released as part of a commercial distribution. Just use those instead of ripping icons from a proprietary product under questionable legal circumstances.