The core processing library (state.mjs), basic visualizer template (basic.mjs), MIDI interface middleware (bridge.mjs) and several pre-written visualizers of Octavia are all free libre software under GNU LGPL license. There is absolutely no warranty for using Octavia, to the extent permitted by applicable law.
Some files came with Octavia are licensed differently, like the bitmap font and voice bitmaps. Read their respective licenses before using them.
Feel free to check the source code out on GitHub. If you like Octavia, don't forget to leave a star!
Documentation is also available here.
See all of the demos available.