What otrahuevada is describing is a situation in which the software developer determines under what terms a particular user may use the software, not a situation where the user makes this choice. Only the latter situation is (can be) dual licensing. The difference may seem subtle, but it's actually huge.

There was a discussion about this with someone else just yesterday. I'll find the link.

Edit: https://news.ycombinator.com/item?id=29871302#29873586