🙏 Do you know if they are building on one of the big open source stacks or are they custom rolling everything?

Custom everything. I don't even know what these are. But I'm sure one could write a nip 99 (or gamma spec) nostr publisher for these solutions if they are what I imagine. Settling the messages invoices would be more complex.

Thank you 🙏 Where's the best place I can learn about gamma spec? It's like an extension of NIP-99? The big stacks are all very pluggable and scriptable. Nostr auth, listings <> NIP-99 all seem doable. I am working out which one to choose and would love to know if any other Nostr apps are built on any of them, which could be good for speed.

GitHub

GitHub - GammaMarkets/market-spec

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It's a NIP-99 extension, yes. Several implementations are linked there but none are building on any of the solutions you've mentioned afaik. Feel free to join the Signal group:

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