Z:gnu-www-ja-selling-exceptions--24d4f5-We must distinguish the practi/en

We must distinguish the practice of selling exceptions from something crucially different: purely proprietary extensions or versions of a free program. These two activities, even if practiced simultaneously by one company, are different issues. In selling exceptions, the same code that the exception applies to is available to the general public as free software. An extension or a modified version that is only available under a proprietary license is proprietary software, pure and simple, and no better than any other proprietary software. This article is concerned with cases that involve strictly and only the sale of exceptions.