When creating a new theme you can/have to pick a parent theme, the new theme will be derived from.
Currently this list is limited to _styled, _unstyled and Classic if I remember correctly.
LFR 6.2.0 RC2 ships with the nice looking and responsive "Welcome" theme.
Customer might want to derive their new theme from this welcome theme. Thus it would be nice if the SDK and IDE could support this.
I tried to pick one of the existing options and then copied the contents of the Welcome theme to my project but at each build the files from the selected parent theme got copied into the WAR file.
As a workaround I edited the build.xml file and removed the reference to the parent theme but I don't think that's a very solid approach for the future.