Since you cannot reliably activate Vuze Plus anymore, here are the top three modern clients that offer the same features (and more) for free or cheap.
Note: If the application throws a connection error during this process, it confirms that the backend activation servers are permanently offline. Best Modern and Free Alternatives to Vuze Plus vuze plus activation code
If you already have Vuze 5.7 installed and want to upgrade to Plus, you can open the activation dialog in two ways: Since you cannot reliably activate Vuze Plus anymore,
Vuze Plus Activation Code & Plugins - Expert Q&A - JustAnswer vuze plus activation code
It uses very few system resources (RAM and CPU) compared to the Java-based architecture of Vuze.
Everything You Need to Know About Vuze Plus Activation Codes