I'm a long time fan of Drupal and created some very complex applications in it.

However, in my current venture I want to use a CMS for the front of end of a enterprise software product, and Drupal's GPL license means that I cant bundle the software without giving away the farm. So despite my love and expertise in Drupal, its goodbye GPL and hello SS's BSD license.

Im interested in anyone with any experience of Drupal 7 module development and SilverStripe. How does low level module development compare between the two systems?

Im interested the SS equivalent of Drupal 7:

1) Entities
2) Hooks
3) Views module
4) WebServices Interface
5) Javascript. Ajax and json callbacks

I wont be doing any content creation in the sense of a standard website, but presenting large data structures called from non MySQL databases inside Flot charting.

The application Im creating wont have many simultaneous users, but it will require some pretty large MySQL tables and entities, that I need to be able to manipulate.

In particular Views in Drupal provides a lot of functionality that can be called with developer API which I need in this project, does SS have equivalent?

Any other tips or suggestions before I start digging into tutorials?

Hmm haven't taken to Drupal myself. Have found the hooks and various patterns messy to work with.
But after reading it won't be a standard site and you're dealing with large data structures.... I wouldn't use Drupal or SilverStripe for a system like that. Firstly nosql support will be limited. Secondly and active recored pattern is hellishly slow when dealing with volume. The performance sacrifice is a reasonable trade off for speed of development with small - medium sized websites.

I would check out lithium for good looking php framework with nosql support http://lithify.me/

In comparsion to Drupal

1: Entities - SS has a cleaner implementation model using DataObjects. A tutorial to get started with is http://doc.silverstripe.org/framework/en/tutorials/5-dataobject-relationship-management. DataObjects create your models, and you're free to developer as many controllers / admin interfaces for those entities as you want

2: Hooks - In 3.0 several ways to do hooks now. The most common use case is DataExtension (http://doc.silverstripe.org/framework/en/reference/dataextension). You'll use the use of $this->extend() throughout the core to allow modules to alter one another. You can also use the new Injector API to allow dependancies to be injected at runtime.

The big change you'll come across is that the tools for SilverStripe are not in the CMS. For things like the views / blocks in Drupal you'll have little CMS control, you'll need to define it yourself.