a hint for us non-US americans: if you intend to localize your package, make the strings in the code US english. Do NOT make them in your default language, de_DE in my case. Reason is, with locale en_US, no translation happens inside Concrete5. It just assumes that you are working in US english. t functions translate from en_US to de_DE, but never from de_DE to en_US.
If thats obvious for you, sorry it was not for me. Didnt find anything on that in the documentation.
Interesting - so you're saying if you create your package in German and then add a language pack for en_US, it won't try to translate it to English for you if you set the concrete5 site to run on en_US?