There's a long long list somewhere. Suffice it to say, about the only thing they share is their aim.
Tint used node-webkit and was more or less chrome + node. Tint 2 is node with a custom bridge and API for accessing native objects. At the end of the day Tint 2 is more performant, security compliant, app store compliant, has more features, and streamlines development immensely.
It depends on the type of application you're developing. It's your choosing.
The MIT license we use allows you to run it or modify it how you chose, and you do not need to disclose any of your source code. The basic version just includes command line utilities which you can use at your own pleasure (and however you wish with no restrictions), the commercial version is essentially the basic one but with a ton of built in goodies to ease development workflows, debug, etc. It also includes a support contract with us.
There is an introduction to Tint in the Getting Started section of the documents and many examples through out the documentation of how to use the API.
If you have an app you've built and would like to show it off, let us know. We'd love to showcase it!