There are a couple of new updates for JKstat and KAR.
For JKstat, version 0.45 brings in JSON support, and 0.50 solidifies it.
For KAR, version 0.6.5 likewise introduces JSON support, and 0.7 makes JSON the only supported data format, superseding KAR's private data format.
The only point of 0.6.5 is that it can both read and write in both the old KAR format and the new JSON format. So I needed that in order to be able to convert old KAR archives.
I've covered some of the advantages of JSON previously. While those were just early thoughts, subsequent tests confirm the advantages of using JSON for both the client-server communication and the KAR archive format. So these releases represent both a transition and a clean break (which is why there are two new versions of each).