You want to use the work of others on your server but dont want to share your own work and help to develop a open source project. Thats your good right, but dont blame us for having given away the ISPConfig sources under BSD license and actively develop them.
42goISP is a paid program, and it is the ancestor of ISPConfig. 42goISP has been written to 100% by projectfarm GmbH and not the openSource community. projektfarm GmbH released the sources of 42goISP under the BSD license and is still the lead developer and largest contributor of the ISPConfig project.
Poeple like you would never contribute to any OpenSource project because it might later been sold as part of e.g. redhat, novell, mandriva or any other partly commercial linux distribution even if the project itself is freely available.
By the way, you asked for IPv6 support, not I. If you dont need it, dont write it.