nobody stops you from using another ERP, they can't use another browser.
They don't own the platform where the ERP runs, apple does.
They don't own the platform where the ERP runs, apple does.
What they don't like is that they have to write some different code on iOS and that costs them money. IANAL but I'd be a bit surprised if "write once, run anywhere" is enshrined in French law.
If Nexedi's product was that good, they could convince people to buy Android devices.
Can a game maker sue Sony because it is extra work to port a game from XBox? Can they force Sony to support Kinect?
Most game consoles since the NES have had lock-out technology, and that's legal everywhere, as far as I know.