Hello Mihai,
I'll try to explain you the things as clear as possible (at least, how do I see them):
1. The "Java Look and Feel Design Guidelines" are just guidelines. There's nothing mandatory in them. They just reflect Sun's view regarding the principles of a good Human-Computer interaction. You can subscribe and follow them (entirely or just a subset) or you can go along with yours, if any. They do not have correspondence in the GUI program's performance, stability nor do they assure you that your application will correctly implement the requirements.
2. The "Java Look and Feel Graphics Repository" represents a set of icons that conform to the above mentioned guidelines. How and under which circumstances can they be used - this is explained in the accompanying license. This license can be found and viewed either:
a) before the download (as far as I remember, you must comply with the license terms in order to be allowed to download an artifact from Sun's website);
b) in the downloaded archive (there's a zip containing a jar, and you'll find the LICENSE file in the root level of that jar file)
And by the way, the jlfgr-1_0.zip is the archive containing those icons which can be downloaded from the 2) page.
Sincerely, I didn't read that license but it should clear to you whether you are permitted to extract the icons and use them individually (that is, embed them in your applicatiob) or not (in this case, you must package the downloaded jar inside your runme.jar). If you read the license and still have doubts, the best thing to do is to contact Sun (both the L&F team at
jlfdesign@sun.com and the address provided at the end of your
SCJD assignment in case if you have questions -
who2contact@sun.com) and ask them.
About the JDK, I'm absolutely sure that you can't just take the icons out of the JDK (again, check the JDK license) nor to rely on them since these are internal mechanisms of the JDK, governed by Sun and susceptible to change in time (just think about the Swing's Windows or Mac look and feels: they're build-in, but IT IS FORBIDDED TO USE them unless you're running on that platform [actually, this is enforced by runtime to prevent misuse]; how do you think that you'll extract an Windows icon and use it on a Unix box without breaking the license terms?).
As for the I18N, this is Java built-in so there's no surprise that Swing makes us of it. It would be surprisingly of not.