Like the previous posters have said, even if its not a scam there are many issues with buying a script programmed by someone else and risking your bankroll BTC to run it on a server.
In the past there were many simple dice scripts which were found online, many people used them and discovered that they were actually being cheated due to exploits in the scripts.
This is why its not a good idea to buy anytype of scripts unless you are going to get the code audited somewhere or do the programming yourself and not start from scratch.
Even if you can find someone for auditing the code, it does not guarantee there is no backdoor for the original coder. These days especially if we are talking about crypto-enabled dice scripts, or now with all the EOS and TRON styled Dapps for casinos, it is difficult to find the guys who know enough technical knowledge to be able to detect all these malicious coding.
Best is always DIY.