This was indeed a problem in the IE6 days. Every browser today (and ES5) supports reserved keywords as unquoted object keys. There are thus no reserved keywords for object keys in ES5, and by extension, JSON5.
No, but there ARE a ton of JSON parsers that expect and require quoted keys now. So it is, in fact, still a requirement. And I don't know about you, you may be lucky, but I still have to make my stuff work on IE6.
