Damien,
This looks like fun!
I'm not necessarily comfortable with an unqualified link from Ingres to
Postgres; can you make it a dotted line or something? The reason I say
this is that Stonebraker was quite firm that there was no code re-use
from Ingres to Postgres, since he was legally prevented from such copying.
Link to my presentation Elephant Roads, which goes over a bunch of the
commercial forks as of 2009:
http://de.slideshare.net/pgconf/elephant-roads-a-tour-of-postgres-forks
Of course, there's been more since then.
And some earlier ones which I didn't know about, like mSQL (and, by
extension, MySQL).
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com