Where can I get Little Generals source code?

You can't get the source code, if it isn't publicly available. There are such things as decompilers, but you really just can't do it unless the devs wanted you to get the code.

You can get the source code from the developer of the app, @smarterapps on twitter. Maybe send them a message with an offer for how much you think it's worth, but the details of the offer or how you ask them to give you a copy of the source code are up to you.