Naturally, Active Directory is the Microsoft enterprise identity access and management directory service and to no surprise, is based on the Windows platform. Therefore, only Windows clients fully support AD. Furthermore, the clients must be Windows 2000 or higher. The Active Directory client can be installed on Windows 98 computers which will allow it to locate domain controllers and services in AD but it cannot be managed with group policy.
There are some integration solutions on the market for Apple/Mac and I believe Linux but your mileage may vary in terms of success with them.