Things you create with Spine are your IP, you own them and you can do what you like, sell them, etc. Those things include your Spine project files and things you export: JSON and binary data, images, texture atlases, and video.

Note that creating derivative works of the official Spine Runtimes (which load and render the JSON and binary data you've exported from Spine) is granted by licensing Spine. So, while you own the JSON and binary data and can sell it, anyone who wants to use the official Spine Runtimes still needs a Spine license.

The Spine Runtimes are not mandatory, anyone could write their own code to read the data exported from Spine and do whatever they like with it, as long as they don't use any code from the Spine Runtimes. That is a whole lot of work though and most Spine users use the official Spine Runtimes. We put a lot of effort into making them good, easy to use, and keep them up to date with new editor features.

To distribute the Spine Runtimes you need to include the Spine Runtimes license. The Unity Asset Store does not allow you to include any other license besides their own, so unfortunately you can't distribute the Spine Runtimes via the Unity Asset Store. You can distribute your own files and you can give instructions on how to get the Spine Runtimes, but you can't include the Spine Runtimes in the files you put in your Unity Asset Store listing.

So to animate with Spine editor and play it with spine runtime you need to buy once spine license? or for runtimes there are separate price?

And lets assume we are 3 people 2 devs one animator. how should we purchase?

Licensing the editor allows you to use the Spine Runtimes. See section 2:
Spine Editor License Agreement: s2

For Professional and Essential licenses, each person using the Spine editor needs their own license. Whoever is creating software products that contains the Spine Runtimes needs a license. Usually that's one of the people using the Spine editor. The Spine license allows them to create any number of software products.

For a business who makes more than $500,000 USD in the past 12 months, a Spine Enterprise license is needed. The license needs to be provisioned for the number of people using the editor concurrently. The license allows the business to create any number of software products during the Spine Enterprise term of one year. The license is renewed annually.

If you create a product containing the Spine Runtimes, you can allow third parties to distribute it as long as they don't modify the product. If a third party needs to modify the product, then they need their own Spine license. See section 2.3:
Spine Editor License Agreement: s2.3

Hopefully you find reading the license text clear. We've worked hard on it over the years to make it as clear as possible. It's of course never fun to read legalese.

SO If I am a developer just using runtimes without even downloading Spine I still have to buy Spine Editor License, right?

Nate wrote

Hopefully you find reading the license text clear. We've worked hard on it over the years to make it as clear as possible. It's of course never fun to read legalese.

love for example section

SO If I am a developer just using runtimes without even downloading Spine I still have to buy Spine Editor License, right?

Yes, that is correct.

Nate wrote

To distribute the Spine Runtimes you need to include the Spine Runtimes license.

Okay, I added it in the detail section on my distribute after I forgot about it.

Nate wrote

Things you create with Spine are your IP, you own them and you can do what you like, sell them, etc. Those things include your Spine project files and things you export: JSON and binary data, images, texture atlases, and video.

Yes, allowing artists/animators to sell their work using this software.