Are you sure you are wanting to have a development server as a subsite of a production server?
A subsite of a production server is still part of a production server, sharing the same db, procs etc. Something breaks in the subsite, it breaks for the production system.
Are you wanting a separate development server on the same ip as the production server?
There are many ways to handle this.
The simplest configuration shares the same domain name, just use a different port, and assign different "subdomain.domains" to both, so there is no confusion with cookies, for example: mysite.com:80 for production and www.mysite.com:8000 for development.
One can also use a reverse proxy to serve multiple domains from the same ip, with each domain serving a separate openacs instance.
