-
InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
It took quite a bit of clicking to find the "open source" part https://github.com/zenorogue/hyperrogue/blob/v13.0/COPYING (GPLv2)
While digging around, it seems there's also an online version for lighter-weight tire kicking https://www.roguetemple.com/z/hyper/online.php
Don't overlook the author's YouTube channel, which digs into the non-Euclidean parts: https://www.youtube.com/@ZenoRogue/videos
NOTE:
The number of mentions on this list indicates mentions on common posts plus user suggested alternatives.
Hence, a higher number means a more popular project.