Has anyone bought open compute gear for internal office tasks such as local file servers, PBX, network services, etc?

It certainly does not seem like it's meant for small deployments, but I'm curious to hear what other have done.

Yes, mostly used units from eBay. Low cost, great performance and reliability. You'll need to make sure you have proper supporting infrastructure as they don't come in standard closed self-supporting enclosures. If you are single-system deployments they don't make much sense, but then again, neither would other rack-mounted systems.

For a while the OCP-Permissive and OCP-Restrictive licenses seemed like they could move open hardware forward, but I don't see as much about them recently. Any idea what's happening with licensing and when OCP licenses make sense for other projects?

Out of interest, does anyone have a ballpark figure for an entire rack of OCP boxes?

Most of the cost would be CPUs, RAM, and storage. I would expect the bare servers to be a small fraction of the rack cost.