no, you cannot use a font in the preview files for which you don’t have an appropriate license.Yes you can There are at least 10 files that do that(including one of mine)
I think we discussed this before, and I believe that the conclusion reached is that a swf with a font embedded is not the same distributing the font (you can’t take it and install/reuse the font from the swf), it’s really just using the font commercially. So as long as you have rights to use the font commercially you can embed them. And those rights are rather easy to obtain, really as long as you have the font on your computer legally you usually have rights to use it even in a commercial setting unless is specifically stated otherwise when you downloaded it. At least that’s what I remember from previous conversations
The FlashDen upload instructions do not say anything about providing a font license for previews. It makes sense that you would be permitted to embed a font in a preview without needing to provide a license, since every website on the internet collectively utilizes so many different fonts, and it doesn’t mean they’re offering that font to people to download it for free.