App Engine vs Force.com

Why did SalesForce decide to create a proprietary language for developing on Force.com?

I have spoken to a bunch of folks who want to move their apps into the Cloud, looked at Force.com and are waiting for Java on App Engine instead, because;

• migration of existing apps (Java) will be much simpler
• Google Gadgets can run on Force.com but SalesForce gadgets won't run on App Engine
• Apps on App Engine will integrate into Google Apps and the security framework to give a seamless User Experience
• App Engine apps can interact with SalesForce if required
• The App Engine 'platform' can be deployed anywhere (you don't have to use Googles App Engine) so if you want to move your App Engine apps to EC2 instead you can (can't do this with Force.com)

SalesForce seem to have gone down the vendor lock-in route rather than the Open/Standards route. This may have given them short-term success, but I suspect that longer term it could restrict the potential of their platform.