No that is highly unlikely (unless you’re doing a lot more stuff on there beyond openHAB).
RAM usage at ~600MB is perfectly normal (although note the part resident in memory is even less).
100% CPU on a 4-core system means 25%, that’s also ok (I assume you don’t run on a 1-core RPi1, do you ?). You would need to see 400% or close to before you may call the system overloaded.
And most of the time when you see 100% it’s one thread blocked and the others idling. Most often this is due to constant reparsing, see this thread for details and a remedy.
