In the news section it is mentioned that Gaffer was disabled because "all currently available versions of Groovy are incompatible with Java 9". This hasn't been true for years now and the latest Groovy 2.5.13 and Groovy 3.0.5 support even Java 15. Gaffer is probably in use by many projects, one being Gretty. It would be nice to enable it again for Logback 1.3.x.