That being said, there are also programmer's layouts specific to single languages which among others have a semi-colon on the home row.

There's no need to use shift to get a semicolon on a french keyboard.

I've never seen QWERTZ keyboard in Poland and I live there. Typewriters indeed were using this layout, but not many people use them to program.

"practically all computers (except custom-made, e.g., in public sector and some Apple computers) use standard US layout (commonly called Polish programmers layout, in Polish: polski programisty) with Polish letters accessed through AltGr (AltGr-Z giving “Ż” and AltGr-X giving “Ź”)." http://keyboard-layout.info/#Polish

Russian keyboard layout does not have any Roman letters so apart from obscure even in their time, Soviet-devloped languages like http://en.wikipedia.org/wiki/Rapira, reaching for shift+4 for ';' is going to be the least of your concerns if you try to write code using Russian layout.

Nitpick: Almost. There is a Dutch keyboard layout, but nobody uses it. Nobody, as in, there's more people in the Netherlands that use Dvorak than people that use the Dutch keyboard layout.

The Dutch commonly use the US keyboard layout, which makes sense because Dutch and English have the same alphabet.