Similar to Gretl

ImpressPages

Info-ZIP

Ingres (database)

Initng

IntelliJ IDEA

Interactive Ruby Shell

Internet Messaging Program

Ipfirewall

Iproute2

IRAF

Irrlicht Engine

Ispell

JACK Audio Connection Kit

Jekyll (software)

Jetty (web server)

Jigdo

Jitsi

JRuby

JSDoc