Yes.

DB-Views offers a free of charge starter license. With this license, you can experiment with all the features of DB-Views. You may permanently utilize your apps and views for commercial applications. You may create application prototypes and demos as well.

Please see here.

Besides of the built-in field validation, DB-Views supports the following input validation methods:

• Text fields can be validated by defining an input pattern. (e.g., zip codes)
• Text fields can also be validated by specifying a JavaScript regular expression. This expression is evaluated whenever the end-user types a character.
• A JavaScript validation snippet can be defined on all field types.  This snippet is executed whenever the end-user types a character providing a powerful and detailed error detection.
• Cross-field validation is done by specifying a form-level JavaScript snippet. This snippet is executed when the end-user submits the form.

You may define money fields in any currency. You may control the field input currency and the currency displayed to end-users. For details, please see here.

You may fully control views and apps user permissions and authentication. Please see here.

Yes. Please see here.