readme: Add status information

README.md

@@ -10,6 +10,10 @@ Niver is a set of 3 network services:
 
 <https://niver.4.niv.re/>
 
+## Status
+
+I plan to create and maintain a public stable instance of Niver, but I haven't done so yet. Thus Niver is not yet tested with real world and long-term usages, and **should be considered alpha software**.
+
 ## Detailed features
 
 ### Public suffix registry (`reg`)