This is a simple Matrix media repo which serves redirects to GIF providers like Giphy and Klipy. It's used by gomuks web's gif picker to avoid having to reupload gifs to the homeserver's media repo.
Despite being called a proxy, this doesn't actually proxy any media, it just redirects the requester to the upstream CDN.
Prebuilt docker images are available at dock.mau.dev/gomuks/gifproxy.
Public instances are available at giphy.mau.dev, tenor.mau.dev and klipy.mau.dev.
The example config is mostly self-documenting and is pre-configured to work with Giphy.
To use Klipy instead, change destination and add split_idx:
destination: https://static.klipy.com/ii/%s.webp
split_idx: [32, 34, 36]