ACL2 is both a programming language in which you can model computer systems and a tool to help you prove properties of those models.

FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created. It supports the most obscure ancient formats up to the cutting edge.

ICal has some complexity to it: Events can be repeated, removed from the feed and edited later on. This tool takes care of these circumstances.

A extension to prawn that allows one to include other pdfs either as background to write upon or to combine several pdf documents into one.

Fungw is a tiny, portable library written in C (C89) that manages dynamic function calls across different programming languages.

A git forge is a site like GitHub, GitLab etc. API::GitForge provides access to some operations which one might wish to perform against any git forge, wrapping the details of the APIs of particular forges. An example of such an operation is forking a repository into the user's own namespace.