It looks real. I am interested in the way they sandbox wordpress extensions, which have been cause of a lot of vulnerabilities, but I am wondering how they sandbox extensions that want more privileged access, like those that replace the content editing and site rendering features.
Well, more like was interested. From their github.
EmDash depends on Dynamic Workers to run secure sandboxed plugins. Dynamic Workers are currently only available on paid accounts. Upgrade your account (starting at $5/mo) or comment out the worker_loaders block of your wrangler.jsonc configuration file to disable plugins.