It's definitely an interesting solution to a very similar problem I was looking at a few years ago - how to take on external investment in a co-operative company.
I'm not in the US, so I can't comment on the options for Nebula, but where I live coops are a specific type of legal company which would encompass what Nebula want - a company where profit is divided between members in proportion to their contribution. As part of that the only owners allowed are contributors, and the only people who can receive a profit share are the owners. If you want to stop contributing you have to stop owning, and there's no value to the shares.
So you can't take on equity funding, only debt.
This structure seems to be made to work around that, structuring it like a regular stock company but with a sale trap to make it unappealing to sell for a quick return.
It depends on what the company is trying to build.
The dollar amount of debt a company can take is limited by its revenue because it requires ongoing payments to service that debt. Whether it's debt from a bank business loan or by issuing corporate bonds, they both require real revenue to make those payments.
Equity investments don't have a ceiling capped by the company's present day earnings. This is important if the company has ambitions to build something that can't get any meaningful revenue on day 1. Instead, they need the money to pay salaries, cloud bills, office rent, etc to build the product and hope the later revenues will justify the investment. E.g. the early Google startup in 1998 took $25 million VC investment and didn't have meaningful revenue until +4 years later in 2002. A company with $0 revenue can't get a $25 million loan with a 4-year deferred payment plan. Yes, there's such a thing as "convertible debt-to-equity" but that's a financial vehicle for investors that doesn't apply to co-operatives.
To remain a co-op, in the sense that most co-operatives operate, they cannot remain a cooperative and take on equity funding from non-contributing parties. There's just no way to do this.
An external party could agree to debt funding with deferred repayments, but they can't link repayments to profit.
Hence the structure of Nebula - a regular stock LLC with a constitution that has an exit trap.
I'm not in the US, so I can't comment on the options for Nebula, but where I live coops are a specific type of legal company which would encompass what Nebula want - a company where profit is divided between members in proportion to their contribution. As part of that the only owners allowed are contributors, and the only people who can receive a profit share are the owners. If you want to stop contributing you have to stop owning, and there's no value to the shares.
So you can't take on equity funding, only debt.
This structure seems to be made to work around that, structuring it like a regular stock company but with a sale trap to make it unappealing to sell for a quick return.