Complex sentence: For instance, Apple Inc. is avid user of this approach by using source code and software from various open-source projects, e.g. the BSD Unix operating system kernel under the BSD license was used in the Mac PCs which are sold as proprietary products.
Split into simpler sentences: For instance, Apple Inc. is avid user of this approach by using source code and software from open-source projects. For example, the BSD Unix operating system kernel (under the BSD license) was used in Apple's Mac PCs that were sold as proprietary products.