Bonjour,
And that is the way it should be ... for now :) For the moment, K2 only works with the "Pro" version of SIG.
Now, "a while ago" (*cough* *cough*), a "certain person" mentioned in a Tweet that the "free" version would be available "any day" :) I, for one, can certainly be very patient as I know that the crew have had their hands extremely full getting the current version of K2 "out the door". Two options for now:
1) wait
2) pony up for "Pro"
Cheers!
Lyle