1. there aren't any legal limitations for creators, TIC-80 is more educational project and you can do what you want with your game
2.
SF X Editor (brief description)
you can define 64 sound effects which also can be used in the Music Editor as instruments
so, we can play 8 octaves each with 12 semitones using predefined Square, Triangle, Saw or Noise wave (or you can design your own wave in Waveform Editor). The whole point of the editor you can change base note frequency, volume or wavetype over time, on the Wave tab you can jump from wave to wave, on the Arpeggio - jump from note to note relative to base note, on Pitch - change base note frequency
just call 'sfx(id)' to run your sound effect
Music Editor
Track is just a table with notes, click on color circle to enable pattern and press Z S X D C V G B H N J M buttons to enter notes