It's just Flow function but alas that works not good with complete cylinder!
In my example that is not a complete cylinder so works fine!


Use : Copy Past in place the top external arc Cylinder (will be the Base curve)
Look at Detail (up page right for have the length of this arc (will be the target line - the same than the script Unwrap Curve )
Draw a line of this length : the Target line

Select the object Cylinder with the window
Call the Flow function
Click the arc Circle (pasted) as start curve
Click the target line drawn
Et voilà you have your unfolded object! ;)