It is a grid, not a set of columns
Every cell on the screen holds a character and a brightness value. Heads run down the columns lighting cells as they pass, and everything else fades on its own timer. Turn the decay up and the trails stretch into proper rain. Turn it down and you get sparse falling dots.
Because each cell fades independently, nothing ever repeats in step, which is why it holds attention longer than it should.
What the characters are
Digits, katakana, and the six letters of the logo dropped in among them. The word surfaces every few seconds, usually broken across two columns, occasionally whole and upright, and once you have noticed it you cannot stop looking for it.
The film used mirrored katakana, which is why the shapes look nearly readable and never quite resolve.
No official version exists
Falling code has been a coding exercise since 1999. It became a search page takeover once browsers could draw fast enough to keep up, so matrix google, google matrix and google matrix 3d all point at rebuilds. The 3D ones add perspective to the same columns and not much else.
Nothing here reacts to the page underneath, which is the difference between this and something like google gravity. The other page that throws the layout away completely is google terminal, and unlike this one it answers back.