You may have a bit of a hard time finding something that’s completely FLOSS that’s not on the older side (the sar visualizer being a Java desktop application being a consequence of that age). There are various ways to dump resource usage into a time series database like Prometheus (Apache2), InfluxDB (Apache2/MIT), or VictoriaMetrics (Apache2) and then visualize it with a frontend (Grafana, APGL). The database is going to be the tricky part. All of the time series DBs I’m aware of are permissively licensed. Grafana may be a good fit for you, however. It’s written in Go so it’s relatively light, although it obviously requires a browser to interact with.