It cannot be denied, Seam was the first system in this area, and also had heavy influence into the development of Orchestra. (But orchestra started different, it started as a tag based system to provide conversations on page level as extended savestate system)
By the time of moving the tag system into lower levels it becamse clear, that at the start of the project Seam was locked to the EJB3 side of things, so the existing tagging system was moved into the domain of Spring 2.0 which had the mechanisms in place to develop custom scopes but lacked a scoping system which provided generic orm control)
Also Orchestra never wanted to achieve the kind of high abstraction on api level Seam provides, it wanted to be a custom scope provider under a very liberal license which others can build upon, and hopefully will.
Also by the time of writing Seam already has provided custom connectors into Spring 2.0. Orchestra probably for the forseeable future will stay on the spring 2.0 side, and it might be possible that it will move out of the jsf centric domain into a custom conversation system for all frameworks. The hooks to plug other frameworks into the project are there, it just is not done yet.