Re: but the suit isn't about content is it.
> IT has nothing to do with using the same images or words (which would be a valid suit) - it's
> only about look.
The specific example cited in the article is expressly about "using the same images [and] words":
"In one particular, a psychology textbook from Macmillan used a photograph of Johann Brahms to illustrate a section on sleep disorders – citing his sleep apnoea. The Boundless-equivalent psychology textbook also illustrates its sleep disorder section with a photograph of Brahms mentioning that he suffered from sleep apnoea."
That's certainly not an issue of "only ... look". It may be that the Boundless text does not use the same image of Brahms, and the same caption verbatim; but what copyright protects - in the US, per USC 17 - is both the expression of an idea (a "work") and derivative expressions ("derivative works"). Derivative works include condensations, editorial revisions, dramatizations, and "any other form in which a work may be recast, transformed, or adapted" (17 USC 101). It would hardly be a stretch, IMO, for the courts to find that Boundless' highly-constrained paragraph-by-paragraph-paraphrase method is a "transformation". For one thing, it'd be possible to automate using existing NLP algorithms, which certainly makes it suspect.
Paraphrase already exists in something of a liminal state between new expression and fair use, and the latter is limited by the amount of original work used and its effect on the market - and Boundless clearly falls foul of both tests. That might well encourage the court to look unfavorably on their process.
USC 17 also covers design rights, by the way, and I suspect it'd be possible to argue that the Brahms example, and even pagination, are covered by 17 USC 1301.
Personally, I think Boundless, if they are indeed engaged in what the suit describes (and that seems plausible), are at least unethical and quite possibly violating the law. They're also undermining the hard work of people who are writing new open-source textbooks.