PixiJS's pixi-spine library uses the official spine-ts runtime, so you will still need a Spine license to distribute PixiJS games that use pixi-spine. You could get around this by not using any official runtime, eg if you wrote your own, but the official runtime is well supported and kept up to date with the latest features. If you make less thank $500k USD per year, Spine Essential ($69) is sufficient to distribute apps containing the Spine Runtimes.