That one is a scanned PDF; its contents don't appear to be indexed by, e.g., Google; its availability is dependent on the continued goodwill of the ACM.

Paul Graham's copy is plain HTML, sitting on the open web where anyone can see it and index it, and while for the rest of us its availability is dependent on PG's continued goodwill presumably he likes being able to rely on it staying there as long as he wants unless he's explicitly forced to take it down somehow.

You have a point. I still find it odd to use a personal domain (other than the author's) for this purpose, with the Internet Archive and other options being available.

What a bunch of lame BS excuses.

Searching for "Computer Programming as an Art" the PDF comes up as the second link (below PG's rip off). Not that it's even relevant because it's given as a direct link.

A scanned PDF is a closer reproduction to the original presentation, and easier to save for later to read.

I trust the ACM's "goodwill" to continue hosting it more than I trust it to remain on PG's website.

> the PDF comes up as the second link

Sure, if you search for its title. But if you search for text within it, you'll find it doesn't come up at all.

> I trust the ACM's "goodwill" [...]

Sure. My suggestion is that Paul Graham trusts his own goodwill more than the ACM's and that that's one reason why he's put a copy on his website.

Knuth is famous for focusing on writing his books. He even stopped using email because it was too distracting. I doubt he has the time (or interest) to export all his writing to modern indexable formats on a site he maintains (Prof. Knuth feel free to yell at me about this assumption). He is clearly credited. Just getting the knowledge out there is good.

What I find truly astonishing is that this 1974 paper is so relavent today.

The ACM copy isn't in archive.org's Wayback Machine due to robots.txt.

Presumably same reason why someone re-tweets something and now it's on their profile. Or he just felt like it.

Generally you somehow point to it.