How are the PaaS offerings of Amazon, Microsoft, and Google closed? You use their API or website to deploy standardized VMs, from which any open-source or COTS software can be used for configuration.
If you build your app around things like Amazon's databases, lambda, etc., then you can't run it (easily) anywhere but on Amazon EC2. It's basically a giant mainframe that runs a proprietary mainframe OS.
Of course you can use a-la-carte VMs in EC2 and do it that way and avoid platform lock-in, but Amazon is increasingly steering users away from that toward managed systems. These managed systems do have short term benefits (just like iOS does), but the long term bargain is similar.
Of course you can use a-la-carte VMs in EC2 and do it that way and avoid platform lock-in, but Amazon is increasingly steering users away from that toward managed systems. These managed systems do have short term benefits (just like iOS does), but the long term bargain is similar.