If algorithm sharing state is "usable" (i.e. executable-only by others), then it should not be forkable on the UI
In the staging, system, the algorithm "AntonioCandia/hist/1" is usable by all, but not readable. So, a fork button should not appear on its list line.
Furthermore, clicking on the said button will generate a 404, since the user has no access to the algorithm code.