Unable to install Lightning 1.9 in Tenfourbird 17.0.2
Tried to tweak Lightning's install.rdf file, but was unable to get Lightning to install.
Tenfourbird is including Lightning add-on. Generally it is enabled automatically.
But when Lightning is installed manually, embedded Lightning are overrided by manually installed one.
This situation may resolve by the following procedure:
Embedded Lightning version is 1.9b1. But this codebase (Jan 05 2013) is newer than 1.9 (Nov 13 2012).
Ok, I understand now. Lightning is built in to Tenfourbird. I don't have to install it manually. And even though the version is listed as 1.9b1 it is newer than 1.9. I was in fact running the embedded version.