MapProxy is an open source proxy for geospatial data. It caches, accelerates and transforms data from existing map services and serves any desktop or web GIS client.
MapProxy is a tile cache, but also offers many new and innovative features like full support for WMS clients.
MapProxy is released under the Apache Software License 2.0, runs on Unix/Linux and Windows and is easy to install and to configure.
Go to https://mapproxy.org/ for more information.
The documentation is available at: http://mapproxy.github.io/mapproxy/latest/