Astrophysics Source Code Library
ascl.net
ascl.net
"Code" and "data" are mass nouns, and have been for decades. You don't say "pass the salts", and you shouldn't say "the codes are" or "the data are" either.
</rant>
That said, I love how open the astronomy community is with their code and data. I wish other fields would follow their lead, but given the incentive structure, they probably won't.
CERN also provide a lot of open physics data from various experiments and is keep adding large amount each year [1]. Of course this still a needle in the haystack but still more than any individual researcher can ever process.
If no one had ever seen more than a dozen grains of sand, it would makes sense to count them and say things like "Sue just showed me her awesome gem collection; she has a diamond, two rubies, and three sands!" But when you are ordering sand by the truck load, that starts sounding really stupid, and you need to shift to measuring it ("sixteen tons of sand") and not counting it ("four million trillion sands").
Mass nouns are measured by giving a quantifier and a unit (three bytes, 64 kilobytes) and do not partake of the singular/plural distinction, which only applies to count nouns.
The British / American distinction is actually easier to explain by saying that they don't partake in the "unitary collective" shorthand; the British parliament are a (countable) collection of politicians, while the US Congress is an undifferentiated mass of...something. The Jury is (are) still out which of these best captures the semantic situation, whereas with code and data we are well past the point where talking about an individual code or datum sounds about like talking about a water or an air.
Also I fully agree with the "codes" rant.
Source: working professionally in the field for 4 years.