Hey, I want to know if there is any way to customize the UI, for example changing the logo etc.., and do I have the right to modify the UI if I want to use it internally ?

The api and ui are licensed under ELv2 https://docs.airbyte.com/project-overview/licenses/license-faq. So I'm pretty sure you can edit the logo without breaking the license as long as you aren't intending to sell the service as a managed service