Given that Guile was basically launched by an RMS FUD attack on Tcl more than 20 years ago, 6 years seems like a rounding error.
Is wikipedia also doing a fud attack on Tcl (as it naturally could be the case), or is RMS post simply a less diplomatic and less friendly way to say that Tcl don't have the same purpose and use case as languages like c and c++? Any turning complete language can of course be used for anything, but looking at how something is used often give a good hint on where its strengths are.
What is not mentioned in that thread (at least not in RMS' original message) is that what triggered his edict was that somebody extended gdb with Tcl as the extension language. This was an absolutely reasonable use case for Tcl - the lightweight syntax makes it perfect as an interactive, embedded scripting language.
This discussion led to the creation of Guile, the withering of Tcl support in gdb, and eventually the introduction of a gdb that used Guile as its extension language — in 2014, 20 years after RMS decided that the Tcl extension (which I believe pretty much worked already) was unacceptable.
Of course, as astute readers will already have guessed, Tcl was BSD licensed...
Of course, as astute readers will already have guessed, Python is permissively licensed.