Updated README to reflect the open license shift for decks

README.md

@@ -3,6 +3,10 @@ opm-data
 
 This is the OPM repository which is supposed to contain all relevant
 datasets and simulation results which are required to test the OPM
-simulators thoroughly. It is a private github repository because some
-of these datasets may not be freely redistributable, although none
-them is "secret" in a more strict sense.
+simulators thoroughly.
+
+Decks are now provided under the open database license, and new decks
+should also be provided under the same or a compatible license.
+
+Note that the git history contains proprietary decks (now removed) where
+usage restrictions may apply.