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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 is Minder, it's open source, free (they accept donations if you're inclined), GTK and not Java. It only runs on Linux as far as I know, you didn't mention what OS you're using, so that might be a problem.
NOTE:
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Hence, a higher number means a more popular project.