You/We/They are publishing. He/She/It has published. I have published. You/We/They have published.

Has published or is published?

Both are correct because Publication doesn't end. So, An earlier version of this chapter was published... indicates that the act of publication occurred at a specific moment in time. An earlier version of this chapter has been published...

Which is correct published on or published in?

This forum post and this one suggest publish in should be used when the place of publishing is a three-dimensional place and publish on should be used when it's a surface.