I just finished a JSON highlighter for Kate and KWrite. It comes with

• folding,

• escape-sequence standout,

• different colors for keys and values and

• basic error marking

The highlighter should work for KDE3 as well and can be downloaded here here.

The screenshot shows JSPF draft code.

JSPF is the JSON counterpart of the XML-based XML Sharable Playlist Format, short XSPF.