The Vuforia SDKs are all free, there are no licensing fees.But there are some restrictions on redistribution and sublicensing of the libraries.
see this forum discussion on this,
https://developer.vuforia.com/forum/general-discussion/use-vuforia-my-commercial-product-free-cost.
https://developer.vuforia.com/forum/qcar-api/commercial-use-modified-vuforia-sample-code