Isn't "orange juice/χυμός πορτοκάλι" what you directly get from the orange, and "orangeade/πορτοκαλάδα" something more processed, with sugar and some other ingredient?
At least in Spanish we make that distinction between "Zumo de naranja" and "Naranjada". And the same goes with lemons, with "Zumo de limón" and "Limonada".
As Theo_Matrakas has said, colloquially both orangeade and orange juice are usually called πορτοκαλάδα. On the packages/bottles you will find 100% φυσικός χυμός πορτοκάλι for a 100% orange juice, νέκταρ πορτοκάλι for a non-carbonated orangeade, and something like αεριούχος πορτοκαλάδα for an orange soft drink/carbonated orangeade.
I totally understand, in czech "limonáda" is also a general term for a fruity soft drink (and the most common is actually raspberry taste, so called "malinovka" = malinová limonáda). But in English (and probably other languages too) "lemonade" is only lemon flavour, which for me is "citronáda". Thanks to the different word root it is not confusing :)
In English, if you end a juice with -ade, it means it is fake/artificially flavoured/not real juice.
For example, orange juice means it is 100% juice from oranges. Orange beverage means it is some combination of mystery ingredients that may or may not even include any actual juice from an orange but should have at least some flavor meant to resemble an orange in part. Orangeade would mean that it is meant to taste like orange juice in some way but likely has no juice from any orange in it at all. So for example Kool Aid is basically a small packet of food dyes and artificial flavors which when mixed with water and sugar makes some sort of sweet beverage. If the Kool Aid is Orange Kool Aid then you could call it orangeade but you could not and would not call orange juice.
But that is not the case for lemonade. For some reason even though -ade is attached to lemon, it is generally understood to be the real juice of a lemon plus water plus sugar.
But I think lemonade is the only -ade that is generally understood to be real juice.
Perhaps this might be different in other countries but I have lived all over the USA and that is what I have always heard and seen.
I have definitely never heard of any such thing as orange lemonade as that would mean mixing the juice of oranges and lemons together. I have never seen that done.