Bill Nelson, has published the “The Most Complete History of Directory Services You Will Ever Find” (until the next one comes along), a detailed history of LDAP based directory services and products. Expect a few updates as people find about this and ask for adding new data points. But this is the most complete summary I’m aware of. I had a timeline of Sun directory products a few years ago, but Bill’s has more details.
His post includes a visual timeline of the directory service products and their heritage, linked here under, for your convenience.
Personally, I’ve been involved with the Sun and derived lines since 1996, and now drive the ForgeRock one: OpenDJ !