It's not free chance you want to look at, but consequence-free as a modifier of chance. This means a chance that is free of consequence.
Let's look at other uses of -free, including a couple of curious ones, for a broader understanding...
The Oxford English Dictionary (OED) defines
-free as meaning
Clear of something which is regarded as objectionable or problematic.
Yes, sometimes a consequence can be 'problematic'.
Other examples from the OED include
There are also
This is similar to one definition of free
Released from ties, obligations, or constraints upon one's action. (OED)
The definition continues
Often used with reference to love and marriage; sometimes also (chiefly Sc.) with the sense ‘unmarried, single’.
The OED offers
fancy-free, which it defines as
free from the power of love
and gives uses from 1600 (Shakespeare) and 1800 (Thackeray)
The Oxford Dictionary online defines it as
Not emotionally involved with or committed to anyone.
Another OED definition of free is
Released or exempt from, not liable to (a rule, penalty, or payment)
"Free from toll; exempt from payment of toll. "
Which does mean 'free from scots' but not 'free from the Scots'. A scot was a A tax or tribute paid by a feudal tenant to his or her lord or ruler in proportion to ability to pay; a similar tax paid to a sheriff or bailiff (OED). So scot-free is not only the literal 'free from this tax' but also
Without being punished; without suffering injury or harm.
So, consequence-free goes along with all these other examples of free from ties, obligations, or constraints upon one's action.