@akumbhare This can be done in latest versions.
It's under Settings > Guest. Just tick allow guest handles. It doesn't ask for an email, just a username.
Nothing to check for the user to upload avatar.
What version do you use?
Please, try to use 0.7+ instead.
git clone -b v0.7.x https://github.com/NodeBB/NodeBB.git nodebb
@APXEOLOG How to fixed it for 0.6.1? I'll update 0.7.x in next week.
I'm don't know, i've only worked with 0.7 version. Are you sure there is such option in 0.6? If so, maybe this is template error