Google has opened up App Engine to one and all.

The cloud-sharing gambit meant to entice developers to build their web applications on the same infrastructure that powers Google’s own applications – and in the process locks them into Google instead of Microsoft – has been in beta for the last six weeks and limited to 10,000 developers.

Google says that another 150,000 developers are on the waiting list and so on Wednesday, the first day of Google I/O, the company’s two-day developer event in San Francisco, it took down the barricade.

Google also disclosed what it’s going to charge for App Engine starting later this year.

The product will be free to get started, and during the current preview release developers will continue to be restricted to the free quota of 500MB of storage and enough CPU and bandwidth for about five million pageviews a month.

Once the preview period is over, they can expect to pay 10-12 cents per CPU core-hour. 15-18 cents per GB-month of storage, 11-13 cents per GB outgoing bandwidth and nine-11 cents per GB incoming bandwidth.

Google also says it will have two new App Engine APIs in the next few weeks: an image-manipulation API so developers can scale, rotate and crop images on the server, and a memcache API described as a high-performance caching layer designed to make page rendering faster.

Every web application deployed is of course a shot at Microsoft.

App Engine is more restrictive than the a la carte Amazon Web Services.

Applications, for instance, have to be written in Python 2.5 and you can forget MySQL and Postgres and other third-party packages.

In exchange developers get access to the Google File System (GFS) and Bigtable, Google’s storage system. Of course users need a Google account to access a service, which may inch them toward using Google Docs and YouTube.

It’s only another step from there to Google-placed AdSense ads. And for trusting Google with the click-stream and user data, a clever developer could get bought.