A library to programatically generate a MultiMC instance from a legacy Forge installer
Call
Installers.getInstaller(yourJarHere).install(multiMcDirectory, yourJarHere);
Head over here and download the latest jar from the assets' area. Once you've downloaded the jar either execute the jar manually or if you would like to be in a CLI mode or are in a headless state, manually execute the jar from the Terminal/Command Prompt via java -jar /path/to/jar --directory /path/to/multimc --jar /path/to/forge/installer.jar