Superhive requires you to connect your account to Blender once before drag and drop works (for every product, not just SpringFX). On your download page press Generate token for this Blender, then in Blender go to Edit → Preferences → Get Extensions → Repositories, select superhivemarket.com (or add https://superhivemarket.com/api/v1/extensions/), turn on Authentication, paste the token and press Check for Updates. Then drag again. Prefer not to connect? Download the zip and drag the file onto Blender instead: it installs straight away. See Documentation, section 2.

Yes. The compiled solver ships for Windows x64, macOS (Apple Silicon and Intel, in one universal library) and Linux x64. The same rig produces identical motion on all three, which is verified by automated tests before every release.

Blender 4.5 LTS through 5.2. If you're on an Intel Mac, 4.5 LTS is the newest Blender you can run, and SpringFX fully supports it.

Yes. Tune the motion in Blender, press Validate for PhysBones, then Export to VRChat PhysBones. You don't need to bake: the physics settings (endpoints, radius curves, colliders and angular limits) are exported.

No. SpringFX adds no helper objects, drivers or constraints to your scene, even with location springs. When you bake, the motion becomes normal keyframes and your other animation is kept.

Free lets you try rotation springs on up to 10 bones. Full adds location springs, collisions, wind, groups, presets, baking, the compiled solver, PhysBones export and free lifetime updates.

If you installed SpringFX by dragging it in from Superhive, it tells you in its panel when a new version is out: press Update and it updates itself. If you installed the zip from disk, download the latest zip from your order and install it from Edit → Preferences → Get Extensions → Install from Disk; it replaces the old version. All future updates are included at no extra cost.