The data is broadcast throughout the Internet until someone says to stop. This is a source based distribution tree. There are many more state requirements than those in sparse mode. Source trees are fully distributed and optimal reverse paths with low delay. In a sparse mode, an explicit join mechanism is employed.
Explicit joins build a shared distribution tree.
The state requirement is probably less and is it not state driven. However, this mode is suboptimal for Interprovider connectivities. Unicast routing is overloaded since it is used for both unicast and multicast, but the mechanism is not the same. A Third provider resource dependency is possible. IDMR Protocol Dave plans build a document with input from folks.