In a heavy, non-reactive, 2½- to 3-quart saucepan, combine the apricots, dates, brown sugar, nectar or juice, vanilla extract, and salt. Simmer slowly, stirring occasionally, until all the fruit is very soft and the liquid is no longer visible, 10 to 15 minutes. (If the fruit is very dry, you may have to add more liquid and cook it a little longer.) Stir in the lemon juice, and cook for 3 minutes to marry the flavors. Remove from the heat, transfer to a medium bowl, and let cool. Mix in pistachios, cover, and refrigerate until cold.