From today, go to the NetBeans IDE download page, make very sure to refresh (i.e., drop your browser cache), and you will see the list of supported languages for NetBeans IDE 7.1:
Note that also the community supported languages, e.g., German, are now in the list, in addition to the official languages supported.
If you choose German, or any other community supported language, you'll get one big download that includes all the localized JARs for all the translations (i.e., regardless of what you choose, you'll get all the languages), and then use "locale", e.g., "locale de" for German, at startup, and then you'll have your IDE start up in the language of your choosing, translated to the extent that it's been translated. For example, here's my German NetBeans IDE 7.1. Click to enlarge the image:
This should be pretty good news, among others for NetBeans Platform developers, who need to deliver their applications in multiple different languages.