It's surprising how little there is about DIALOG around HN (or maybe it isn't, an old outlier sort of thing, also very hard to search the common word)

Here's one of the few resources collecting some of the history - "DIALOG History" https://dialoghistory.org/home/

Their own obit:

https://dialoghistory.org/2026/07/11/the-online-search-world...

https://en.wikipedia.org/wiki/Roger_K._Summit

non-paywall: https://www.nytimes.com/2026/07/17/technology/roger-summit-d...