iRedAdmin Pro- The amount of licenses needed in different OS

==== Required information ====
- iRedMail version:
- Store mail accounts in which backend (LDAP/MySQL/PGSQL):
- Linux/BSD distribution name and version:
- Related log if you're reporting an issue:
======== Required information ====
- iRedMail version:  iRedAdmin Pro
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: Ubuntu & FreeBSD
- Related log if you're reporting an issue:
====
Hi~Zhang, I would like to make a test with iReadAdmin Pro between Ubuntu and FreeBSD.
First of all, I will install and operate it on Ubuntu ,which is a testing environment.
Then, clear off and install on FreeBSD(in the same server equipment) .
How many license should I purchased??? Thx.