Anyone wanting to write a client in a non-html technology (like iOS, or Windows, etc) is taking on a significant risk: either you have to host the json converter on your own server, or you have to hope that wms hosts the json server on the kgs server.
Running your own json converter is fine for development, but I would not want to run it in production. There are hosting costs (compute+bandwidth) with no apparent means of income, unless you charged for the iOS or Windows apps, which sounds like a legal minefield. Furthermore, if there were technical issues, you'd have very little means to resolve them. The json converter is closed source, and you would have no access to the binary logs.
Realistically, you'd have to hope the 2nd scenario happens - that someone writes a good enough html client that persuades wms to host the json converter on the kgs server itself.
It has been suggested to embed the json converter inside the client application. An interesting idea, but since this requires Java itself, it may make the installation footprint enormous, not to mention complicated. It does suggest an obvious direction tho - perhaps someone can write a better Swing client
