Based on the actual architecture, we can do something to meet this need.
We will add a new setting on each project: Open Project. If this is set, you will be given a unique link with an invitation page where visitors can signup to one or more language versions of the terms. This way you won’t have to add them to the project as collaborators and they will be able to assign themselves to the translations they choose.
It should be ready in less than a week.