Is it possible to play Project Yavin IV mod on english version of Kotor? I know Polish so knowledge of language won't be a problem.
Yes, you'll just need to convert the local sub-strings of the GFF files. You can use tk102's DLG Language Converter, it won't convert the contents of the dialog, however you'll be able to read the Polish it's written in. You can get it from the Star Wars Knights website. (starwarsknights.com)
It's unfortunate that the author hasn’t released it yet. Though he works very slowly, so I can't be sure. Apparently now he's working on an M4-78 project, though I'm putting more stock in the M4-78 restoration.