You need license only for developers. End users does not need a license. Developer is defined as a human being who writes a code which uses Rebex API.
Distribution of your application (which uses Secure Mail DLLs) to any number to end user computers is free (as long as every developer who is using the Secure Mail API is licensed).
Difference between editions are as follows:
1 developer license
- 1 person can write code which uses the Rebex API
- 1 person can develop software using Rebex API on unlimited number of computers
- your application which uses Rebex API can be installed on unlimited number of computers.
5 developers license
- 5 persons can write code which uses the Rebex API
- 5 persons can develop software using Rebex API on unlimited number of computers
- your application which uses Rebex API can be installed on unlimited number of computers.
Company license
- every developer in a company can write code which uses the Rebex API
- every developer in a company can develop software using Rebex API on unlimited number of computers
- your application which uses Rebex API can be installed on unlimited number of computers.
More info can be found in Shopping and Licensing FAQ: