If I use the BYOB 3.1.1 Compiler to convert a project to .exe, am I allowed to sell discs with the .exe file on them? If so, what sort of credit do I owe BYOB?
Yes, you are allowed. Look at the copyright notice in the About box for the copyright credit.
But, BYOB3 is so old, and so buggy, and so slow! I wouldn't want to sell a product using it.