I believe Dymola is correct. delay is a vectorizable function, but OpenModelica does not support calling it as such. The following works:

block Variable3Delay "Delay block with variable DelayTime" 

  extends Modelica.Blocks.Interfaces.MIMO; 

  parameter Real delayMax(min=0, start=1) "maximum delay time"; 

  Modelica.Blocks.Interfaces.RealInput delayTime;

equation

  for i loop

    y[i] = delay(u[i], delayTime, delayMax);

  end for;

end Variable3Delay;

I'll see if I can solve it easily.

In this OM beats Dymola! Indeed, if I submit your code to OM, it works; if I submit it to Dymola 2012 I get:

Error: Current version of Dymola cannot deduce indices for for-loops.

Your code modified in only the for statement as follows:
       for i in 1:nout loop

works in both environments

Massimo

In OpenModelica r10002+ the syntax in the initial post works.