In addition to the varieties of open source and free software licenses already discussed, there are licenses that do not fall within the Open Source definition but incorporate some elements of open source principles. The Sun Community Source License (SCSL) is one such license, developed by Sun to incorporate some of the benefits of open source development into two proprietary Sun products, Jini and the programming language Java. Sun has been very careful not to characterize this license as an open source license; the license clearly is not such a license. The most important distinction between this license and open source licenses is the Sun-imposed compatibility requirement. While users are free to modify the licensed work, they may not deploy modified versions of that work without compatibility compliance being certified by the licensor, i.e., Sun. This puts substantial limits on the applicability of the open source model to Sun's project. Such restrictions may, however, be justified by Sun's desire to ensure that Java maintains its cross-platform portability, which incremental tweaks in individual versions could quickly undermine. In addition, commercial use of the SCSL-licensed code may require the payment of a royalty, which is, again, inconsistent with the open source model.

Despite the fact that the SCSL is not an open source license, it embodies an innovative licensing principle—lying somewhere between the classic proprietary and the open source ...