How can I use old theme with 2.10?

A similar question was already asked but not answered yet. Therefore, I’d like know how to upgrade to 2.10 while keeping the “old” theme?

Not answered?

This is the official recommendation from NETWAYS and/or ICINGA?

The official recommendation to those not liking our themes was always: Write your own. Even if it is based on the old one. It’s an open-source project after all.