```ruby
cask :v1 => 'dwarf-fortress' do
  version '0.40.24'
  sha256 '653837ed073ffe2825d25bc80f0967d6a8ccb9bf869a188d4bd4320154630936'

  url "http://www.bay12games.com/dwarves/df_#{version.sub(%r{^0+\.},'').gsub('.','_')}_osx.tar.bz2"
  name 'Dwarf Fortress'
  homepage 'http://www.bay12games.com/dwarves/'
  license :unknown    # todo: change license and remove this comment; ':unknown' is a machine-generated placeholder

  suite 'df_osx', :target => 'Dwarf Fortress'
end
```

Update license for Dwarf Fortress to 'gratis'.
user
```ruby
cask :v1 => 'dwarf-fortress' do
  version '0.40.24'
  sha256 '653837ed073ffe2825d25bc80f0967d6a8ccb9bf869a188d4bd4320154630936'

  url "http://www.bay12games.com/dwarves/df_#{version.sub(%r{^0+\.},'').gsub('.','_')}_osx.tar.bz2"
  name 'Dwarf Fortress'
  homepage 'http://www.bay12games.com/dwarves/'
  license :gratis

  suite 'df_osx', :target => 'Dwarf Fortress'
end
```
assistant