Numilog is being sold back to its founder and CEO, Denis Zwirn. Hachette hasn't discussed the terms of the sale but they do plan to keep using the platform. It currently offers more than 50,000 titles.
I'll be honest and say that I'm not familiar with their services, but based on the ones mentioned in the press release (digital file distribution, direct or indirect sale of digital books, creation and administration of ebookstore site) I would hazard a guess that Numilog offers services similar to txtr, a German ebook startup which was bought back in 2010 by 3M.
If I'm correct then perhaps Hachette Livre took too long to part with Numilog. Txtr is already powering a dozen or more ebookstores in Europe & South America. They're moving much faster than Numilog, who might struggle to keep up.