hjson is new on my radar, but looks like it has some great philosophical overlap with KSON! hjson's "interface for JSON" tagline really resonates. If I understand correctly, hjson helps by not requiring commas, allowing unquoted strings, and supporting multi-line strings. Our support is similar, though we only use # for comments instead of // and support multiline strings both in embed blocks and regular quoted strings.

Where KSON diverges from hjson is enabling a YAML-like presentation while improving on the YAML experience. And by making the content type of embed blocks a first-class citizen of the syntax, with clear boundaries for the embedded content, editors and IDEs can provide full tooling support (syntax highlighting, validation, etc.) for the embedded code. Importantly though, KSON remains 'plain data'---it's not a runtime that executes code in your configs.