Hello,
I’m happy to inform that an updated pl_PL translation for OJS 3.1 is available for download from here:
https://szmigieldesign.pl/files/ojs-31-pl_PL-19-03-2018.tar.gz
The latest translation is a direct successor of our previous work and was thoroughly checked and edited by my colleague Ewa Rozkosz. It’s complete for Open Access journals and includes translations for plugins installed by default with OJS.