Setting up a development board in parallel with an active board?
 

o/

Historically, vB updates have broken custom themes. It's been a while since I've worked with vB, but talking to current owners, this is still a strong tradition moving into 4.0 from 3.8/etc. In the past, I've worked around that by having a private dev board hidden by htaccess where I ironed out kinks and rewrote themes/features until the board looked and functioned with the site as intended. The updates were then migrated over to the main board with a short downtime. This prevented disruptions in the active community board from occurring at every available patch that had the possibility to last weeks at a time.

The new EULA seems to forbid this without having to purchase a second license. So how are site devs able to work out the integration of their forums without purchasing that second license? Is there some sort of "setup mode" that lets you run off a db mirror? Perhaps vB allows board operators to run a sandbox along with their active board? It'd be a huge deal breaker if I couldn't ensure my community or clients would be able to visually operate unaffected by backend patches.