It seems to me it's just folk humor without specific author.
There was famous concept 'voluntary slavery' (добровольное рабство) from french philosopher which was discussed by famous russian writer Lev Tolstoj, but it has nothing relevant to dachas.
However folk humor seems to bind this concept to dachas by it's nature of 'voluntary slavery' and sometimes 'voluntary' is omitted.
Satirical cartoon is very probable because it's really fun.
If you still want to make some sign, you can write 'Is dacha voluntary slavery or forced rest?' as a joke.