Invoice Ninja: add NonFreeNet (see MaintainerNotes)

metadata/com.invoiceninja.app.yml

@@ -1,3 +1,5 @@
+AntiFeatures:
+  - NonFreeNet
 Categories:
   - Money
 License: AAL
@@ -735,6 +737,9 @@ Builds:
       - $$flutter$$/bin/flutter build apk
     ndk: r20
 
+MaintainerNotes: server soft uses Elastic-2.0 license which is approved neither by
+    OSI nor FSF, see https://invoiceninja.github.io/docs/legal/license/
+
 AutoUpdateMode: Version
 UpdateCheckMode: Tags ^v.*$
 UpdateCheckData: pubspec.yaml|version:\s.+\+(\d+)|.|version:\s(.+)\+