In todays modern landscape big coorperations want you to rent not buy. Stream not own.
That is why I will never charge a dime for anything since I am a firm beliver that not everything people spend their time on has to have a profit incentive. Or be turned into a giant money making buisness.
For .it or "impulse tracker" files OpenMPT will work and is what I use, but any tracker in general will do as well.
These modules are for people to enjoy and maybe for people who are new to this artform anf want to learn and get inspired and by that I mean you can use these in whatever you want as long as its not used for any commercial (spotify, buisnesses, what have you) stuff and remains free for everyone to use.
And some credit would be nice but not necessary ;)