The use-cases could be, for example, payment processors storing customer data, encrypted webmail (where you're able to search w/o downloading all your emails), "encrypted evernote" :-)
Yes, it will be open source once available
Yes, it will be open source once available
Thanks for the good work guys, best of luck with your project and (ad)venture.
Having the index end-to-end encrypted imposes some limitations though. You have to do several requests when you want to do one query which is obviously slower. Though, still practical.
And since the CPU logic happens on the client, in some cases (many simultaneous clients) the performance can be actually better.