Janus is making use of Nxt blockchain and moves to Ardor as a child chain when this goes live in Q3 this year.
https://bitcointalk.org/index.php?topic=1677509.0Janus made betterbets.io and are working on other web applications that connect to the blockchain or not (depends on the sort of site)
With investing in Janus you can earn dividends that are payed in Janus token.
This is what i understand about it.
Nxt is a blockchain platform that is here since 2013 with great builtin features.
Ardor is an improved version of Nxt which solves scalability and bloat issues every blockchain project faces and no one except Ardor solved. With ARDR tokens you secure the network by forging and earn the transactions fees of all child chain bundlers (new role in Ardor)
IGNIS is the first child chain of Ardor platform which mainly will be used by the community and devs.
If you hold your NXT during the single snapshot on Ardor mainnet live that you will get free 0.5 IGNIS tokens for every NXT held.
1NXT = 1NXT + 0.5 IGNIS
Hope this helps a bit.
Otherwise join slack for a quick chat
Nxtchat.herokuapp.com