When considering buying a game development product. the questions you must first ask are A)How much would it cost me in both time and money to instead outsource development of my own component.
B) Can I extend and modify the code to suit my own purposes.
Some answers for you.
1) Development time of a fully functions interaction system, with voiced content/ storyboards , sound effects etc can be create just by you in at leas 30 minutes if you want well structured content. outsourcing and development would take a few weeks or months if the system is being built from the ground up.
2)Yes, you can modify all of the code used in game. and you can create your own extensions. If you want hands on help then you will get that help.