The appeal of these engines is based primarily on the success of the original game. While the audience may be receptive and enthusiastic, there is the risk that successive titles will have similar look and feel to the original or that the genre will be dated and no longer compelling by the time a subsequent title is released. The success of the original game often allows the provider to charge a high price for the engine as well. The main advantage of an object license is that it is typically less expensive than a source license. Not having source forces the developer to ignore lower-level details and concentrate on issues strictly above the interface.
Game developers are typically very savvy.
The ability to view the source provides an understanding of the engine that can be valuable to wringing the most performance possible out of the engine and simplify debugging of the title. Source code also allows customization if there are particular, unusual requirements for a title. Finally, there are two primary pricing models, royalty and royalty-free. This model is very appropriate for a startup organization that has little cash, or for a very special-purpose title that is likely not to sell many copies. The key advantage is that there is no additional impact on profits should the title become a big hit.