I'm pretty sure it's the other way around, and Microsoft has similar agreements with most of its partners. Ubuntu's however, is a free OS, so any cloud hosting

I'm pretty sure it's the other way around, and Microsoft has similar agreements with most of its partners. Ubuntu's however, is a free OS, so any cloud hosting can use it without major repercussions even without any support contract with Canonical. Any cloud provider that doesn't like this agreement, doesn't have to make it.