i just tried with the latest gideros' gtween (note that it is edited 10 days ago), and use this sample (i took the sample from your link and add sprite definition, also include a image file in project) and it works(the callback is called) :
local animate = {}
animate.y = 100
animate.x = 100
animate.alpha = 0.5
animate.scaleX = 0.5
animate.scaleY = 0.5
animate.rotation = math.random(0, 360)
local properties = {}
properties.delay = 0
properties.ease = easing.inElastic
properties.dispatchEvents = true
local sprite = Bitmap.new(Texture.new("box.png")) -- ADD THIS
stage:addChild(sprite) -- ADD THIS
local tween = GTween.new(sprite, 10, animate, properties)
tween:addEventListener("complete", function()
stage:removeChild(sprite)
sprite = nil
end)