I wouldn't call it theft, exactly. Presumably work did get done. If I'm reading it right, its just a terrible conflict of interest. The board uses donations to pay companies to work on LibreOffice. That seems totally fine. Some of the board were running/part of companies that rely and work on LibreOffice. That also seems mostly fine? You want your board to represent your community. Then, those same board members directed work towards their companies.

That's definitely a conflict of interest, but I wouldn't call it theft unless you prove the foundation was getting a bad deal. Could the foundation have gotten the work done better or cheaper hiring non-represented companies? That's the question you have to answer to call this theft.

It doesn't seem that is really what the foundation is arguing though, so I'm guessing it wasn't that bad. It seems more their argument is that this violates the non-profit laws they operate under.

It's a kind of corruption referred to as "self-dealing."

As directors of LibreOffice, they should be looking for the best deals for LibreOffice. Contractors (or any employee) are always (logically and reasonably) looking to do the least amount of work possible for the most compensation possible, so if as a director you use yourself as a contractor, your duty opposes your interests.

And if on the one hand you're being paid a flat salary (or no salary at all) for making decisions for LibreOffice; and on the other hand the worse the contracts you make with yourself are for LibreOffice, the more income you will receive, plunder is absolutely inevitable.

This is exacerbated even more with some nonprofit who is answering to an amorphous public who is funding it. They have no way of stopping you, other than withdrawing entirely.

At the very least it looks very much like corrupt conduct, even if it isn’t.

No. They did the work. It is a corrupt practice, not theft