That looks like what you would get if you asked it to install in the same directory you downloaded it to.

It would try to copy lib/ into itself, resulting in your "lib/tke/lib/tke/lib/tke/..." mess.

Like:

  $ mkdir lib
  $ mkdir lib/tke
  $ tclsh
  % file copy lib lib/tke/lib
  error copying "lib" to "lib/tke/lib": "lib/tke/lib/tke/[cut off long string here]": file name too long

Specify a root directory other than the current directory and it should work.

I wonder if tcl should disallow copying a directory into itself.

Edit: I opened a bug report for tcl: https://core.tcl.tk/tcl/tktview/82049f96f841214bb8cee18e1bf8...