I tried to find the info in the Whitepaper, but could not see it covered there. If the the Dune tokens were airdropped to Tezos holders, it means that the dev team did not get any funds. Where will the dev team get funds for development as the platform looks very complex.
In landing page of website linked in opening post (
https://dune.network) you can find the link to their whitepaper.
You are right about the fact that no ICO/IEO took place so no money collected.
Cannot answer about the financial resources of the team.
What I know is the team behind Dune project is a French engineering group, OcamlPro, which is the team who initially worked at Tezos development. Then they parted from Tezos Foundation for some, let's call them, misunderstandings and created Dune.