The following sentences are copy from tclkit official site: 
https://code.google.com/archive/p/tclkit/

                                         2016/01/31 nwp8861
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License

The Tclkit-specific sources are license free, 
they just have a copyright. Hold the author(s) 
harmless and any lawful use is permitted.

This does not apply to any of the sources of 
the other major Open Source Software components 
used in Tclkit, which each have very liberal 
BSD/MIT-like licenses:

IncrTcl, Metakit, Tcl/Tk, TclVFS, Zlib

