Great job! But I do wonder: is there a reason for not integrating in Lightning network (or plasma itself)?
Would it take mich effort?
One of the advantages of L2 is cross chain interoperability.
Final question: can we have a view on the team behind?(is it linked to the funding of emin gun sirer?)
What's important to understand is that just like lightning doesn't change the Bitcoin protocol, something like Marigold wouldn't change the Tezos protocol.
A L2 (Layer 2) solution is typically built as a highspeed network on top of the protocol (L1) with possibly entirely new functions. You basically sacrifice some security / decentralisation / censorship resistance to do this, but only at the L2 level. The L1 level stays the same and can function as a settlement layer.
This way you open Bitcoin/Tezos up to fast, cheap transactions, when high security etc. isn't needed, fx. for the famous/infamous cup of coffee that's always used as an example of (against) the usability of blockchain for day to day payments
I suppose Tezbox could integrate it, if many people started using their app for coffee-like payments. But it requires that the shop accepts the specific L2-solution as payment, not just XTZ.