A method and apparatus for enforcing software licenses for resource libraries such as an application program interface (API), a toolkit, a framework, a runtime library, a dynamic link library (DLL), an applet (e.g., a Java or ActiveX applet), or any other reusable resource. The resource library can be used by authorized end user software programs. A “per-program” licensing scheme for a resource library can allow a resource library to be licensed only for use with particular software programs.