Hi Robert,
Is there such an online tool or website which allows for transfering team licenses?
Yes, Creative Cloud for Teams comes with an admin console where this can easily be performed. It's a very simple process. You revoke the current user's seat. Their software will revert to trial mode and no longer be connected to your agreement. Their seat will now be freed up in your console to allocate to another user.
Can the team members be at different locations?
The geographic location of your end users will not be an issue with regards to console management.
How often is a license transfer possible (eg. once a month, week etc).
As often as you'd like, there are no restrictions.
Is an unistall required in order to move a license? Or would the tools simply deny to start until a license was assigned again?
No uninstall needed, the seat will be deactivated as soon as you revoke it in your console. The user's software will go into trial mode. It can, however be reactivated should you choose to re-deploy to the same end user at a later date.
I hope this helps!
Zach