From: Eric Dantan Rzewnicki [mailto:rzewnickie@rfa.org]

My understanding is that apps need to follow a certain model (call-back base processing vs. block processing, iiuc) in order to function properly within the jack graph to meet it's low-latency and synchornous execution requirements. There were some pre-existing apps that fit this model and some that didn't. The authors of some of those that didn't fit rewrote their apps or wrote new ones. Some other authors either didn't care about jack's goals or disagreed with them and so their apps aren't jackable. I don't think there are any behind the scenes political maneuvers going on to keep certain apps out of the jack family.