Help now works.
I downloaded the precompiled version of Gimp 2.0.6 from the Slackware-current
archives, downloaded the 2.0.6 help files, installed them and now Gimp has
help files, including a limited amount of context-sensitive help. Hooray!
The default help-browser is Mozilla, which is a royal pain. I frequently have
multiple browser windows open at the same time. Mozilla has this huge
roadblock where you have to fire up a different profile for each instance of
the browser.
So I will switch my default help browser to Konqueror which has no such
impediment. I wrote to the Mozilla folks on this issue but they seem dazzled
by the brilliance of their creation, and never mind what the users want or
need.
I also downloaded the 2.2 tarball but immediately found myself in the library
chasing game. So I will hold off on that version until the Slackware folks
offer a precompiled edition.