I've been looking at the DropBox Mac client and I'm currently researching implementing a similar interface for a different service.
How exactly do they interface with finder like this? I highly doubt these objects represented in the folder are actual documents downloaded on every load? They must dynamically download as they are needed. So how can you display these items in finder without having actual file system objects?
Does anyone know how this is achieved in Mac OS X?
Or any pointer's to Apple API's or other open source projects that have a similar integration with finder?
Two suggestions:
The former will allow you to write an app that appears as a filesystem and does all the right things; the latter will allow you move everything server-side and let the user just mount your service as a file share.