One type of open source license is the LGPL. The LGPL is used for licensing program libraries. When evaluating the LGPL there are issues concerning whether a user should statically or dynamically link newly created programs to LGPL libraries.
A user creates a new program by writing source code, which often includes comments ignored by the computer to explain how the program works. It reveals trade secrets on how the program operates with other hardware and software, and may contain information on how to maintain the program’s confidentiality and security. After being created, the source code is run through a compiler in order to create object code.
A library means a collection of pre-written functions or data that other programs use.
A program (linker) can combine a library with another program, creating a single new program. If the library and the program are separately installed, and the program is configured to link at run time with the library, the new program, when it runs and finds the library, does not need to be subject to the LGPL. This is dynamic linking. When a dynamically-linked program is executed, the links between the pre-existing LGPL library routines and the created program are resolved at runtime without copying any of the code into a new executable. Though there has been no case law on this subject, the prevailing view is that when the new program is distributed, the libraries are not actually incorporated. It is the end user that creates the derivative work, but the copyleft concept requiring source code release under the LGPL would not apply at the instance of the end user because there would be no distribution by the end user.
However, if a program incorporates the library code, the new program would be subject to the LGPL requiring source code release under the copyleft concept. This is static linking. The separate bits of source code are combined to create a single executable program. A derivative work is created based on the existing libraries.
Though there has not been any case law on the subject, because the LGPL requires the release of source code and prevents users from establishing proprietary rights in the works when a program incorporates a LGPL library, there is prevailing opinion that a company that uses open source library products in its manufacture of proprietary products for commercial distribution should ensure that its own products are not statically linked but dynamically linked to any LGPL library if its main business model is to generate revenues from license fees.
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