If he's a user he can request the source code which they'll be required to provide per the terms of the GPL. The litigation kicks in if they don't comply. Whet

If he's a user he can request the source code which they'll be required to provide per the terms of the GPL. The litigation kicks in if they don't comply. Whether Rossmann is the copyright owner or not is a minor point given he could throw his money and expertise behind whoever is.