Firewall use requirements

Answer: I'm assuming that by the terms "Open source" and "License" you mean a firewall that is free of charge or paid .

Considering that, ISO 27001 is not prescriptive about how a firewall, or any other control, should be implemented, so organizations have freedom to choose the implementation that better fits its needs, provided that the solution is used in accordance with the license terms associated therewith (even open source firewall may have license terms that must be followed).

This article will provide you further explanation about using firewalls:
- How to use firewalls in ISO 27001 and ISO 27002 implementation https://advisera.com/27001academy/blog/2015/05/25/how-to-use-firewalls-in-iso-27001-and-iso-27002-implementation/

This material will also he lp you regarding the use of firewalls:
- ISO 27001 Annex A Controls in Plain English https://advisera.com/books/iso-27001-annex-controls-plain-english/