Thanks for the info, but I said ubiquitous exactly because I need something that "just works" on each one of Windows, Linux, Android and iOS. And I'm not aware of any open source solution there, hence have to use Wuala.
IIRC, Boxcryptor isn't specific to iOS, I have it running on OSX at home, and I believe it also runs on Windows, though I've never had a reason to put it on my VM.