Actually, if I've got my facts right, they were BOTH WELL LATE to the linux party :-)
iirc, Pick Systems were actually *selling* their D3 database in 199*6*.
This came in two versions, plain D3 running on Red Hat, and D3-native where Pick replaced the userland so the user didn't see linux underneath.
(obTopic - Informix were later reverse-taken-over by a Pick-alike vendor - six months after taking over Ardent, all the Informix guys were gone and the Ardent people were running the show with their UniVerse and UniData databases ousting the Informix database as the main product(s) of the company)