SQLite: Protégé of PostgreSQL

AFAIK SQLite doesn't achieve atomicity by virtue of its global write lock. It does so by using a rollback journal (default) or WAL. So it's not really all that different from PostgreSQL in that regard and the authors point remains valid :). You might also enjoy this talk by the main author of SQLite: ▶ this video (SQLite: Protégé of PostgreSQL)

Not sure about a 30 year timeframe. 10 years seems like it wouldn't be any kind of problem (personal opinion), but 30 years is an awful long time. That being said, the SQLite development Community are very very big on backwards compatibility. eg: ▶ this video Hmmmm, there's a better talk by D. Richard Hipp around, but I'm not finding it atm. In the better talk he explains they (SQLite) are planning to be around for the 30 year timeframe you mention. Something to do with an airplane manufacturer looking for long term guarantees, but I don't remember the details.

As a read-only database, sqlite doesn't have too many limits, since the storage mechanism is flexible enough to allow fast queries. The problem comes when you start writing, and reads have to wait for them. Also, (I believe) it was this talk ▶ this video that mentions sqlite being used in adobe lightroom, and it being faster to access thumbnails from an sqlite database.