Lighting Network is a trustless protocol
Can it operate on it's own, or does it need to be a layer on top of a cryptocoin network?
What incentive do LN node operators have to operate?
https://cdecker.github.io/lightning-integration/
It runs on top of Bitcoin-like Blockchains that have segwit or something comparable.
If you run a LN node you can charge fees for routing payments.
The most expensive step would be opening a channel, but there is work on reducing that cost.
But right now this is still VERY early in development.