This is such a ridiculous accusation. Why do discussions about source-available models often turn into accusations of soliciting free labor? Why can't authors just provide access to source code, but reserve some or all of the distribution rights? It's their code, after all. Nobody is forcing 'the open source community' to contribute under the terms set forth; anybody who does contribute does so under their own free will, under the terms set forth by the license.
It doesn't always have to be a binary choice between open source and closed source, nor does it justify further accusations of "openwashing."
Without that, I don't see how this is open-washing...
>The Winamp Collaborative License is a free, copyleft license for software and other kinds of works.