(disclaimer: i used to work at spideroak, but not on the crypton project)
I would chalk this up to R&D. I don't think they'll make any money off of Kloak but they do want to bring crypton (the framework on which Kloak is built: https://crypton.io/) into maturity. Another project of note associated with crypton would be the password manager Encryptr (https://spideroak.com/solutions/encryptr). I'm not sure they want to replace their backup/storage service with crypton (although their backup service could use more collaborative features, so R&D into crypton could improve that), but they probably are looking into building other privacy focused products on top of which a better/mature/battle-tested crypton would be necessary.
Not to mention: if everything is encrypted using your password as a key, how do your friends see your posts? Are they encrypted for each friend with that friend's public key?
They could be encrypted with a random symmetric key that is then itself asymmetrically encrypted individually for everyone in your network and provided to them through some means. This is also how the OpenPGP works.
This seems buried. Is there a reason it's not mentioned or linked on the kloak page? I actually went looking for the code and couldn't find that repository.
I figured it was likely in the app, but for an experiment like this, that appeals to many of the ideals of an open source philosophy, I'm less likely to bother installing it if I'm unaware that it's an open source project.
Obviously the appeal ultimately needs to be greater than just being open source, but that initial bump can't hurt the outcome of the experiment.
Aside of the closed-source aspect, that is a great way to run a secure peer-to-peer messaging platform / social network. I believe this is how iMessage also encrypts communication.
Earlier in the thread I mentioned that Kloak came about as a UX experiment in private social networking. We are building on these concepts in another project that is underway now.