If you are a Linux user, you really need to check out
elementary Icons by ~
DanRabbit. This absolutely amazing pack contains 1,000s of vector icons which can be used to replace almost everything! ~
DanRabbit's Elementary Project is definitely worth checking out! (
Suggested by `Alexander-GG and Featured by
`BurgerBunny )
If the icons stay as separate, unmodified files, then you're good. (Doing that and, for example, loading the icons at runtime as toolbar icons in a program just counts as aggregation, not making a derivative work.)
If you modify them, you have to share the results under the GPL (eg. images and videos which contain them, new icons based on them, etc.) but you're still OK to use other licenses for things that are merely distributed alongside them.
Caution: I am not a lawyer. These are just the details I've seen real lawyers agree on.
I put up a more detailed explanation, a general explanation of how to fix the problem manually, and a script for doing it automatically on my blog. [link]