What about the CO2 cartridges? Sodastream has attempted to stop people using third parties to refill them by using a weird connector. Is that not similar?
That must be quite a while ago. I have a Sodastream and have been using non-Sodastream CO2 cartridges with it for at least 5 years.
What they have tried to do is when you exchange your empty cartridges for a full one, they will only accept Sodastream cartridges. However, 3rd party cartridges are available quite readily everywhere.