Hi jamiejame11,
Based on my understanding, if you use Skype for business Trail Version you don’t need to CALs.
If the Skype for business trail version expired, you need to contact Microsoft buy Skype for business CALS.
Moreover, you could use SFB basic version, please refer to
https://www.microsoft.com/en-us/download/details.aspx?id=49440
Here is a similar case for your reference
https://social.technet.microsoft.com/Forums/en-US/51ef53c9-f9ac-4eee-96ae-f599353e9ebe/skype-for-business-server-trail-and-cals?forum=sfbfr
Regards,
Alice Wang
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