First of all:
Thank you for contributing a new translation and providing detailed information.
Regarding your issue: The line
'powered' => 'Powered by the Open Source Social Network.',
MUST NOT be translated -
see the last the paragraph of
"II. WHAT YOU SHOULD KNOW IN ADVANCE" in https://www.opensource-socialnetwork.org/wiki/view/2132/how-to-translate-ossn
Last not least: Please note that all Ossn components have their own 'locale' subdirectory with translation files. Thus, you have to add a
ossn.id.phpfile to each of them in order to get your site completely translated.