Although mountains do meet, this proverb is expressive. :)
There are some things or events in life that are believed to be impossible, like an encounter between mountains, but there is always a chance for people to meet.
The proverb can be interpreted in a positive way, showing how easy it is for people to socialise and meet more often, but it can also be interpreted in a negative note saying that one can always find a possibility for revenge. "We'll meet again!!!" :)
Here are some early mentions of this proverb:
1530: Palsgrave, L'esclarcissement de la langue francoyse, 635: "Hylles do never mete, but acquaintance do the often."
1754: Berthelson, Eng.-Danish Dictionary, 29: "Friends may meet, but mountains never greet."
Origin:
Afghan proverb widely used in Afghanistan and it sounds like this: KOH ba KOH namerasa amma AADAM ba AADAM merasa. It means mountains can't help each other but humans can. (Abdulrab Tarshi Dari, Pashto, Uzbek and Turkish Linguist).
Mali me mal nuk piqen, njeriu me njeriun piqen.
Translation: It is the mountains that do not move to help one another; but one man surely comes to the help of another.
Basque
Mendiak mendiaren behaŕik ez, bainan gizonak gizonaren bai.
Translation: It is the mountains that do not move to help one another; but one man surely comes to the help of another.
Bulgarian
Планина с планина не се срещат - но човек с човека.
Translation: A mountain never meets a mountain, but a man meets a man.
Catalan
Les persones es troben, les muntanyes no.
Translation: The people meet each other but the hills do not.
Esperanto
No venas mont' al monto, sed homo homon renkontas.
Farsi
کوه به کوه نمیرسه ولی آدم به آدم می رسه
Translation: A mountain never meets a mountain, but a man meets a man.
Frisian
Bergen moetsje inoar net, mar minsken wol.
Translation: A mountain never meets a mountain, but a man meets a man.
Irish
Casar na daoiní ar a chéile, ach ní chastar na cnuic.
Translation: The people meet each other but the hills do not.
Karelian
Mägi mägenke ei yhty yhtei, a ŕištšikanz ŕištšikanzanke yhtyu'.
Translation: Stones do not meet stones, but a face meets another face.
Maltese
Ġebel ma' ģebel ma jiltaqa', izda wiċċ jiltaqa'.
Translation: Stones do not meet stones, but a face meets another face.
Persian
Kuh be kuh nemi-rasad; âdam be âdam mi-rasad.
Translation: It is the mountains that do not move to help one another; but one man surely comes to the help of another.
Polish
Póra z górą się nie zejdzie, ale człowiek z człowiekiem zawsze.
Translation: A mountain never meets a mountain, but a man always meets a man.
Plaj plajeça ći maladōl, rrom rromesa.
Translation: Mountains and valleys stand firm but people meet.
Romanian
Munte cu munte nu se-ntâlnește, dar om cu om se-ntâlnște.
Translation: A mountain doesn't meet a mountain, but a man meets a man.
Deal cu deal se întâlnește, dar om cu om.
Translation: A hill meets another hill, of course a man meets a man.
Munts e vals stan salda, ma la glieud s'inscuntra.
Translation: Mountains and valleys stand firm but people meet.
Russian
Гора с горой не сходятся, а человек с человеком сойдется.
Translation: A mountain never meets a mountain, but a man meets a man.
Scottish
Coinnichidh na daoine far nach coinnich na cnuic.
Translation: The people meet each other but the hills do not.
Turkish
Dağ dağa kavuşmaz, insan insana kavuşur.
Translation: Hills remain apart forever, (but) people do meet (someday).
Ukrainian
Гора з горою не зійдеться, чоловік з чоловіком - завжди.
Translation: A mountain never meets a mountain, but a man always meets a man.
Veps
Mägi mägemu î soite, a meź meśtmu soidise.
Translation: Two men will meet sooner than two mountains.
Welsh
Cynt y cyferfydd dau ddyn na dau fynydd.
Translation: Two men will meet sooner than two mountains.
