Update README.md (#1185)

Update language describing iperf2 vs. iperf3

README.md

@@ -100,11 +100,10 @@ submit an issue.  Please use one of the mailing lists for that.
 Relation to iperf 2.x
 ---------------------
 
-Note that iperf2 is no longer being developed by its original
+Although iperf2 and iperf3 both measure network performance,
-maintainers.  However, beginning in 2014, another developer began
+they are not compatible with each other.
-fixing bugs and enhancing functionality, and generating releases of
+The projects (as of mid-2021) are in active, but separate, development.
-iperf2.  Both projects (as of late 2017) are currently being developed
+The continuing iperf2 development
-actively, but independently.  The continuing iperf2 development
 project can be found at https://sourceforge.net/projects/iperf2/.
 
 iperf3 contains a number of options and functions not present in