In other words, we could now produce our 1948 standard of living (measured in terms of marketed goods and services) in less than half the time it took in that year. We actually could have chosen the four-hour day. Or a working year of six months. Or, every worker in the United Stares could now be taking every other year off from work-with pay.
In a way I've managed to make that choice. I currently work four hours a day on paid work; over the past 8 years that's been my average thanks to taking several years mostly off work.
Of course things are really more complicated, since I spend a lot (often more than four hours) of my leisure time on technical "work" that's just as demanding (if less stressful generally) though not done for money, and since there's a definite bleed over between what I'm working on on my time off now and what I'm likely to be paid for doing in a couple of years time.
The article suggests that we would need to cut our desired standard of living in half to work half time. While mine is probably lower than average, it's not that much lower, at least for this area; I have to make up the difference by being a more desirable employee than average, and part of how I do this is "banking" my contributions in my free time. This is an aspect of free software that many people don't seem to get, that your contributions can pile up over time and end up being personally beneficial later.
Of course health care is really problimatic when working a reasonable amount of time, such as four hours, in America. You have to budget at least 3/4 your health care costs to be paid yourself, not as a benefit. Working in Europe begins to seem really attractive, etc.