OpenStreetMap.org and many other web map tile servers are using
renderd with Mapnik to generate and render raster tile images and
mod-tile with Apache2 to make them availabe by serving them on a webserver. For example for providing a slippy map on the web. They are an essential part of the classic raster tile map software stack of OpenStreetMap.
renderd are Free and Open Source Software with their code available in a public repository.
renderd are mainly written in C and C++ and have been been actively implemented from 2007 to 2011 by a group of contributors. The last release was nine years ago when I assumed responsibility for maintenance, at the same time there were also many good code suggestions waiting in the pipeline as pull requests on Github.
Through a broad and constructive collaboration among Free and Open Source Software contributors, we were releasing two versions in the first year and we were able to reduce the number of 31 open pull requests to under 10 and applied a good amount of additional bug fixes, code improvements, documentation and general clean-up. The number of open issues is down to under 40 from over 80.
Packages for Debian and Ubuntu
Together and with the support of the Debian GIS Team we wrapped them up as Debian packages and made
renderd available in the official repositories. Starting with the release of Ubuntu 21.04 (hirsute) and Debian 11 (bullseye) the software can be conveniently installed from the built-in software sources.