The TL;DR is as follows:
It is implemented on top of another cryptocurrency with smart contracts. (Not really familiar with this, taking it as a cons.)
Uses a WoT for both issuance (must be verified by three existing members to join like #duniter) and settlement (payment can only be done by chaining trust, like #Ripplepay / #Rumble http://ripple.ryanfugger.com/ )
Seems to be a good starting point against sybil/fake ids attacks.
Since credit is limited by trust, there is an incentive to balance income and expenditure like a credit-based #LETS / #LocalExchangeTradingSystem plus the UBI means it could be non-deflationary and incentivize usage rather than savings as in facilitate economic transactions while being an #universaldividend token.
Sunbeam City is a Libertarian Socialist solarpunk instance. It is ran democratically by a cooperative of like-minded individuals.