There will be a beta program. We’re still working out the details of how we’ll administer it, but you’re very welcome to be a part of it! There will be an ‘early beta’ before we receive our cross-signature from IdenTrust, when the certs we issue will not yet be trusted, and a regular beta after we get the cross-signature. Participating in the early beta would only be suitable for test sites, or sites that currently have no HTTPS and are okay serving an untrusted cert temporarily (because in theory no one visits their HTTPS version).
Once we get the cross-signature, certs issued in the early beta should become retroactively valid, but will need some web server configuration to serve the new intermediate certificate.