Use uwosh.pfg.d2c (https://pypi.python.org/pypi/uwosh.pfg.d2c/)
It's an adapter for PloneFormGen (I know you said you don't want to use it, but keep reading). It transform your data in real Archetype content and you can enable an optiona that make it works with anonymous users.
And it will work on Plone 3.3. also.
Another approach is our unreleased collective.signupsheet (https://github.com/RedTurtle/collective.signupsheet) that is based on uwosh.pfg.d2c, but it's focused on event subscription. However we never released it (use at your own risk).