I have and FAQ point that addresses this here. Quoting from the site:
What happens if Recall disappears one day?
It is understandable that there is some hesitation to invest your time into adding your information to a new application and the obvious fear that it may just disappear one day. I want to reassure you that we are fully committed to Recall for the long term. But in the unlikely and unfortunate case that Recall doesn’t work out we will ensure that there is more than enough time for users to export their data so that it can be moved to another application. We would also open-source the project to allow users to host Recall themselves.
What happens if Recall disappears one day?
It is understandable that there is some hesitation to invest your time into adding your information to a new application and the obvious fear that it may just disappear one day. I want to reassure you that we are fully committed to Recall for the long term. But in the unlikely and unfortunate case that Recall doesn’t work out we will ensure that there is more than enough time for users to export their data so that it can be moved to another application. We would also open-source the project to allow users to host Recall themselves.