Does UrbanTurtle interfere with other tools from Microsoft, other vendors or that we could have developed?

No, Urban Turtle does not interfere with any tool.

Again our goal in designing Urban Turtle is that it seamlessly inserts itself in the TFS ecosystem. To achieve this, we decided to rely on standard extension mechanism and not have a separate data store. Urban Turtle directly manipulates work items using the standard APIs.

This allows us for example to validate the workflow transitions in the task board even if you customize your workflows. Also, since you customize your work item fields using standard mechanism and Urban Turtle does not add extra data, the powerful reporting and data warehousing capabilities of TFS will not be affected and will work as documented by Microsoft.