Actually, OpenCPN works on MANY operating systems, but not iWhatsIts. And if you're going to be working with satellite imagery (KAPs or mbTiles) to augment your charts, then you probably want to run it on a real computer anyway.
From the OpenCPN web site Download Directory: "OpenCPN is free, open source software for marinenavigation. It is available for Mac OSX, Microsoft Windows, GNU/Linux, BSDs and Solaris." I suppose Mac OS is not the same as on an ipad. What a shame, hello Aqua Maps!