This list also includes games in which the engine is open-source but other data (such as art and music) is under a more restrictive license.
TD,sandbox Only the game engines in this table are developed under an open-source license, which means that the reuse and modification of only the code is permitted.
As some of the games' content created by the developers (sound, graphics, video and other artwork) is proprietary or restricted in use, the whole games are non-free and restricted in reuse (depending on the content license).
It could also be the prevention of a commercialization of a free product in future, e.g. when distributed under a non-commercial license like CC NC.
The video game remakes in this table were developed under an open-source license which allows usually the reuse, modification and commercial redistribution of the code.