Complex sentence: Early services such as CompuServe and The Source added optional simplistic graphics-based programs (GUIs) to present their information, though they continued to offer text-based access for those who needed or wanted it.
Split into simpler sentences: Early services such as CompuServe and The Source added graphics-based programs to present their information. Early versions provided a simplistic GUI, though they continued to offer text-based access for those who needed or wanted it.