flag of the American People's Republic
This flag is something of a recreation of a flag I saw on here some time ago (though its source has long since faded with time), but with a little flourish of my own added.
This flag uses the Serapis flag, also known as the John Paul Jones flag, which was a flag that was improvised by Dutch port authorities. Jones had sailed into port in a flagship he had captured during battle (since his original flagship was sunk). Jones was a privateer (basically a pirate) that served the revolutionary cause, sinking British vessels and freeing slaves wherever he went. I personally adore how the stripes basically break all rules of proper flag design, and how it also had both a semi-historical link to the American Revolution but also is just obscure and odd enough that reactionary nationalists simply cannot claim it.
The emblem on the canton is, of course, the emblem of the Minutemen from Fallout 4. In this case, the rifle symbolizes freedom and the willingness to defend it, and the lightning bolt symbolizes action (as in "we're not just talking, we're acting.")
As for the stars: the red star of course symbolizes socialism, the green star symbolizes ecology, and the light blue star symbolizes liberty.