[Victor Wagner] is working on
[http://www.45.free.net/~vitus/ice/tcl/unixhelp.html]
a "help viewer for Tk on [Unix],
which would work ..." with .chm.
In Victor's words, "This package provides [platform]-independent  viewer for context-sensitive
hypertext help build from same sources as [Windows]-specific .chm files.
Compiler to build unixhelp helpfile from [microsoft] .hhp HTML Help
Workshop project file is also provided.  [[The]]
Tcl programmatic interface is compatible with Christian Werner's 
[winhelp] extension ... Imitation of the Window Help viewer functionality is almost complete, at
least for needs of my projects."