I'm surprised nobody has mentioned the most obvious (and innocuous) motivation: to expose young developers to google's cloud platform so that they'll be comfortable with it when they become big-time CTOs in a few years.

The network effects for cloud services are nowhere near as strong as they were for operating systems (end users don't care which underlying platform is used) but there is an advantage to having more developers familiar with your service.

This makes the most sense to me as motivation for this kind of give-away. Both familiarity to soon-to-be-promoted techs, as you said, and establish themselves as the system to migrate AWAY FROM.

To have the first $100k of server time's code written on their platform is not meaningless. Perhaps I'm a sub-par wizard, but host migrations are a very real pain point in my experience. With $100K's worth of time spent developing on Google's platform, that pain would be pretty well developed by the time a startup would get around to worrying about it.

Yes, I think it's clear that this is not charity, but spending <=$100,000 on EXTREMELY well-targeted advertising.

Google gets a customer and free advertising, the company gets 100k worth of free computing resources. It's called a "win-win." It's not quite a "free lunch," but it's "one of the main ways in which healthy business gets done."

Not to nitpick, but the site states $100K for 1 year, which seems like a "use or lose" type deal. So if your start up doesn't burn through that much in hosting/storage/computing, you aren't really getting $100k in free computing resources.