Is Open CTI integration (Call center) available for all Salesforce clouds (sales, service, marketing, health etc).
Where can I find information about which modules/integrations/features are supported by various SFDC clouds?
Yes, Open CTI is available in all "clouds", as long as you're using Essentials, Professional, Enterprise, Performance, or Unlimited edition. I'm trying to find documentation to support this, but all I've come across is this forum post from 2013. Sorry!
The short answer is Yes.
Open CTI is a framework to integrate third-party CTI systems with Salesforce.
Open CTI integrates third-party CTI systems with Salesforce.
So as long as you have the following editions, you will be able to integrate Salesforce with any third-party CTI system. From documentation:
To display CTI functionality in Salesforce, Open CTI uses browsers as clients. With Open CTI, you can make calls from a softphone directly in Salesforce without installing CTI adapters on your machines.
Available in: Essentials, Professional, Enterprise, Performance, Unlimited, and Developer Editions
Once you have integrated the CTI systems using Open CTI, and when you want to extend the implementation to any particular feature in Salesforce, that's when you will need a particular feature/license type.
E.g., if you want to integrate the solution with a call center, that's when you will need Service Cloud licenses because you will need those licenses to build a Call center application.
After you develop an Open CTI implementation, you can integrate it with Salesforce using Salesforce Call Center.
In all other cases, as long as you have the licenses for the aforementioned editions, you can build your integrations using Open CTI.
As a reference, below is what I found over web while searching around this topic, which confirms this behavior. You will find more details around the integration using Sales cloud as a reference on the same link.
When NewVoiceMedia first designed its CTI integration with Salesfore, it used Salesforce’s existing Salesforce telephony integration API to allow NewVoiceMedia’s cloud-based telephone to communicate with Salesforce’s sales and service clouds.