Hello and welcome on this board.
First thing I want to say, it's no need to post 4 times in 3 minutes as it's one story.
To come to your story.
- In the Netherlands it's prohibited to release sky lanterns, some people may think different about this issue but it's what the Dutch Law says so! For festivals etc.. there's a possibility, you could ask for a special license, weeks before the event, with some instances.
- At Firework shows or events, there would also be other circumstances. They would need to forfill to that special licence and I'm affraid the insurrance companies wouldn't be that happy, because the lanterns will come down to earth again but not on the shooting terrain but far outside.
- You're posting in the international forum, the above just counts here in the Netherlands, the rest of the world is a complete different story. For example Germany, or the U.K. What I've heard it's free to release the lanterns, offcource several miles away from airports.
My personal opinion is, that's very nice to use the lanterns with firework displays. For example the Loy Krathong festival in Thailand. At this festival (full moon) people will launch thousands of these lanterns, also known as Khom Loi, at the same time. It really gives you a amazing view, some people also add some small fireworks under the lanterns, effects like a silvery tail. At the same time there's a fireworks display. Really amazing and I hope to see this in the near future in Europe also. Here's a small video with some fireworks and lanterns in it, it's taken at the Loy Krathong festival.
http://www.youtube.com/v/_tNHscNxn_U