That's not free, it's just a workaround that lets you avoid paying money.
And I mean that the concept is an interesting one, but the way they've done it is crap - as I said, it's slow, jiggly, and limited; you can't organise the words - they spring back; it's really slow; you can't have multiple webs on the screen at one time; clicking stuff takes too long; it only shows a limited number of synonyms; and did I mention how slow it is?