OxWall regularly checks for updates to the kernel, plugins and themes. Also check that the licenses are valid.
If the OxWall server disappeared, you would be automatically not informed of the updates and you would have to find another way to install plugins and themas.
This will require modifications to the OxWall core
I don't know what the other developers will do. I suppose in the event of a catastrophe, the majority of those that remain will be lost.
I suppose that if OxWall disappears, all or part of the Copyright rights are lost, the legal part of all this should be studied.
For my part, I will continue using OxWall and try to convince developers to offer a free patch. The initial idea is that the plugins already installed continue to work and to install a new one a license number that the developer would assign to be validated on the server of each developer is required, or if they do not want or can have a server for this, they simply yield a list of their assigned licenses to be validated on the developer server they want.
I do not think this scenario is necessary, SkaDate uses this same system for its licenses and I do not see that they are against OxWall, I only see that they have lost interest.