@vinney posted about this back in April of last year, but it didn't get much attention (#941440). Looks like there is a reference client now:

Anybody on Earth can participate in Catallax and nobody can be stopped from doing so by anyone. Those who choose to participate in Catallax do so as one of the following roles, depending on their goals:

• Patron: Creates tasks to be worked, finalizes agreements with Arbiters, funds escrows and assigns Free Agents.
• Arbiter: Advertises as an escrow agent, accepts tasks, judges outcomes of work and pays Free Agents or refunds Patrons.
• Free Agent: Applies for available tasks, delivers work and gets paid.

Arbiter advertisements, Task postings and their eventual resolutions are posted on the Nostr protocol while payments are handled via Cashu ecash and Lightning.

Thanks to Cashu-based wallets and Nostr’s permissionless identity creation, anyone (namedoxxed or nym) can participate in the Catallax economy without conforming to KYC or AML nor first having a Bitcion or Lightning wallet configured.

All you need is a web browser.

These kind of things are hard to launch. Do they always require a huge spend at the beginning to get the critical mass necessary to make it worth using? As far as I remember, things like AirBnB and Uber absolutely dumped money into advertising and onboarding in order to make the product work. I'm not as clear about the history of craigslist -- maybe that got momentum by being hyper local? I'm curious how stackers would go about getting something like Catallax off the ground.

Also, I love the name.