In the question text it is written:
Different major versions of the same language are considered unique. So, your code can be executable in Python 2 and Python 3, however Python 2.5 and Python 2.7 are not considered unique.
I believe that Python 2 and Python 3 are recognized as being almost two different languages. For instance, the results of this challenge shows that there are 46 and 34 answers in Python 2 and Python 3 respectively. There are probably a lot of answers where the language is only listed as Python, but there are relatively few compared to those were the version number is included.
In comparison, there is only one Mathematica, and I've never (or rarely) seen anyone specify which Mathematica version they are using.
Although there are functions that can only be used in some versions, I'm not sure they should qualify as different languages.
What is the community's view on this? Both in general, and with regards to the Versatile Integer Printer challenge.