Re: "merging it with an unlisted Luxembourg entity"
Er.... it's a Swedish private equity fund doing the puchase.
The "merger" is probably just a device to ease the delisting process. Changing a company to private ownership can be quite complex, it's much simpler to pretend it was taken over by another company.
Best case scenario is that the plan to face off Red Hat would be considered too risky for a listed company which has a duty to not engage in strategies the could bust the company.