Another way to describe it is: instant and infinite development machines for open source projects that you could pull out and throw away as cheaply as tissues.
You click the button, you get an IP address and password and login as root. All the code and dependencies are installed.
The target user would be someone who wants to play with a project, but is weary of installing it on their local machine, or perhaps they are on windows and there's problems. The second target user is someone who wants to contribute code to a project but doesnt want to setup a local dev environment. The third target user is just the normal dev who wants to try what it feels like to use their software with a fresh install.
Perhaps the user could add their credit card info to upgrade an ephemeral instance into a persistent one if they want.
It should be instant, so a project can have a queue of VMs on standby ready to assign immediately. You could use the Digital Ocean API to keep the queue primed. The open source project could have a small budget (say $15/month to always keep 3 available on average). You could maybe adjust the # of free VMs in the pool via a simple backend either interace or API url.
Bonus points if it could also launch VMs on Azure, AWS, and/or Google Cloud.