OwnCloud is primarily a DropBox clone which also provides the ability to install "apps" on top. Those "apps" are perhaps better described as "plugins" -- they a

OwnCloud is primarily a DropBox clone which also provides the ability to install "apps" on top. Those "apps" are perhaps better described as "plugins" -- they augment the OwnCloud interface using code which (as I understand it) runs inside the OwnCloud server. Apps must be written in PHP and there is no sandboxing or access control to prevent a bad app from doing bad things. In contrast, Sandstorm apps are isolated by default and can be written in any language. Sandstorm does not provide a shared "filesystem" but rather gives some private storage space to each app and then expects them to talk to each other via RPC if they want to share data. We (the Sandstorm team) are actually thinking of porting OwnCloud to Sandstorm as an app. :)