What Acquia offers us?
- Acquia Drupal - Acquia's enterprise Drupal distribution. It is Drupal plus several contributed modules plus Acquia Network integration module.
- Acquia Network - Subscription plan for various Drupal enhancement services (e.g. spam blocking, update notification)
- Support and customization service - as usual
It is easier to explain Acquia's business model using Red Hat analogy:
- Drupal = Fedora; standard general distribution for everyone
- Acquia Drupal = RHEL; comprehensive distribution for some people
- Acquia Network = RHN; subscription service in compliment with RHEL
Drupal is open source, Acquia Drupal is also open source. Everyone can download them for free and has freedom to tweak them like all other GPL software. However, Acquia Network is not free (that's how they make money), like RHN. Fortunately, Acquia is a startup company and they have free trial period for Acquia Network that everyone can try.