Hello to everybody,
It's my first post in the forum although I've been visiting it for long. My name is Constantinos and I'm from Greece. I live in Thessalonica. I'm posting to express my willingness to contribute in case you believe I can, in helping with Greek translations.
Like it was stated before, Hellenic (or Greek) language hasn't changed so much through the ages. It's true that "Kathareuousa" is still spoken in Greece by members of the Orthodox church and scientists related to language and linguistics. It's a form really close to the medieval Greek for the reason that only the "public-form" of Greek really changed through the last centuries. In fact, even a "good student"-teenager can fully understand texts written in ancient or medieval Greek directly from old-stones, temples, sculptures etc.!!!
Also, the easy part is that in Greek there are no accent problems. Of course, there are territories (like Crete, Cyprus) where you can spot differences, but the mainland's accent is clear and hasn't changed. In other languages, like German or English, people of different origins have developed through ages their ways in speaking it. Austrians have a more "rough" way, for example. In Greek there is no way of doing it. All vowels and consonants are so specific, there is no "a" that can be spoken differently like in "father" or "age".
The only thing to be checked is the "h" letter when Greek words are written in English. For example, "Hoplites" -> Oplites -> Οπλίτες (the ones that are armed with weapon) Oplon -> Όπλον is Weapon. In "kathareuousa" and "modern Greek" we do not pronounce the "h" like a soft form of K (KH). We say Oplites. English do so. The matter is that the English say it like ancients did! In ancient times they did that. In kathareuousa there is mark (tone) to indicate that O should be spoken like Ho (the mark is called daseia if I´m not mistaken) although speakers ignore it and in modern Greek there is no clue for anything like that. Most of young people don't know that English kept alive parts of ancient Greek because of the fact that nobles and teachers used to study medieval Greek in universities or through books. Maybe some other differences between medieval and "kathareuousa" should be found before you continue in Greek translations and acting-thing but I'm sure they are tiny ones.
Should you need anything please inform me. As a student of the university of Thessaloniki I have access to thousands of books related to the medieval Greek language and historic matters.
Thank you for reading this looooong letter...and I apologize for its size!