Complex sentence: Thus, a proprietary version may be released of an MPLed open source program--for example, Netscape Navigator versions 6 and 7, which are proprietary versions of corresponding releases of the Mozilla Suite.
Split into simpler sentences: Thus, a proprietary version may be released of an MPLed open source program. For example, Netscape 6 and 7 are proprietary versions of corresponding releases of the Mozilla Suite.