I think an MMT framing works well here. They give you $40. You're not explicitly required to list in the bulletin, but presumably for practical purposes you do

I think an MMT framing works well here. They give you $40. You're not explicitly required to list in the bulletin, but presumably for practical purposes you do need to be in the bulletin to participate in this economy. So you're effectively taxed $6 per six months to continue participating in this economy. So it is a kind of debt obligation but one that's voluntary, like a tax you can choose to forgo. It reminds me a lot of Warren Mosler's Buckaroo experiment; they give you the money, then tax you, and your need to pay the tax causes you to sell labor denominated in that currency. (I'm having trouble finding a text source for this, but they described it in an interview here https://youtube.com/watch?v=LCUPBpSiISU https://youtube.com/watch?v=LCUPBpSiISU)