-
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.
There’s Nitter, but I’m not sure if it supports some sort of following system.
Mastodon? I don't know much about them but according to their website it's open source. I vaguely remember seeing a few developers using it instead of twitter
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.