No. Cyberduck is fully functional for free. A is provided as a gesture of gratitude to those who contribute a minimum of $10 USD to support the project. Key benefits of registering include:

: One key can be used across multiple computers owned by the same person. Official Download & Installation

Instead of risking malware from third-party "crack" sites, you can safely download the latest version of Cyberduck through its official channels: : Download Cyberduck .