Cloud computing will be based on unix infrastructure
though opensource is not going to be the be all and end all here.
If a company creates let's say an email client on the cloud, they don't have to opensource and why should they?
You can write a closed application and run it on a system with a Linux kernel.
You can even use GCC and some of the LGPL libraries and not open source it again (though alter a LGPL library and you have to release that alteration).
All software is about service, the service to entertain, inform, make tasks simple, or even just possible. To maximize your profit, you need to protect your service niche by making it harder than someone just copying your code and jumping on in, then they can offer the same service but not pay for the development costs, so they could probably undercut you.
And have a look at most opensource stuff, most consumers don't want to use it, it is not designed for them, it is designed for developers. Sure, a few developers get lost in the idea of opensource as some type of revolution, but that pretty much stops when the consumers who are paying nothing, start coming in and demanding x and y feature :)
Opensource, works because if a developer wants a feature he/she can roll up their sleeves and include it. Not many consumers are willing to do that.
The GPL is even more confusing to most consumers, but really that is just about a little convention dance amongst developers, companies who don't understand the GPL and use GPL code often get stung, though of course they are often just asked to comply. But failure to comply stops them using the software, so can be quite expensive.
Though, to drive cloud computing you need a solid base, and that will be unix, and quite right you won't want to pay licensing on the base so you will look to make that opensource. And that is the right thing really, consumer applications closed in the main, base infrastructure open, and development tools open. Someone has to pay the ferryman and that is the consumer.