Hi,
As per below compatibility matrix, Cisco 4331 supports 100 SIP Phones with recommended DRAM and Flash Memory:
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucme/requirements/guide/cme126spc.html
Other than CME licenses, you don't need any other licenses. But I would recommend you to test third party SIP Phones thoroughly with CME and see if it meets all your requirements.
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Thanks, Vaijanath S.