Good catch, I'll have Alex take a look. Could you create a jira for 4.0 and attach the patch?
Yes, that is a bug. I took a look for similar attribute in jsf-api and found that it uses 'forValue' as enum name while it returns "for" in toString method.
Seems that I have to check attributes for Java keyword and switch to similar solution if property name concurs with Java keyword.
I've created JIRA issue for that: https://jira.jboss.org/browse/RF-8898
Why adding "Value" suffix for java keywords only? Just add it to all property keys. Your solution is better then mine, because it doesn't involve and require user to know what's under the hood.