Browser Lock locks code to a list of browsers. This will ensure that the code will only work in one of the allowed browsers. This is a good transformation to enforce license agreements. Countermeasures can be specified (optionally) to be executed when the code is executed on an unauthorized browser.
Consider combining this transformation with obfuscation transformations to harden the resulting code making it more resilient to automated de-obfuscator tools and harder to understand by a human. You may also find useful to combine this transformation with other locks: