We're happy to discuss general licensing here on the forum. Email is better if there is anything more sensitive to discuss that you'd prefer not to be made public.
The Spine Runtimes license is here:
https://esotericsoftware.com/spine-runtimes-license
It provides 2 options: 1) license the Spine editor which grants more rights, or 2) each user of your Product must license Spine. Most apps and game use #1. Some OSS, libraries, and similar use #2.
The Spine editor license is here:
https://esotericsoftware.com/spine-editor-license
Section 2 defines the terms for the Spine Runtimes.
terry-kk I noticed that the Spine runtime itself is open source, and the license has no restrictions on commercial applications.
This is incorrect. The source is publicly available but it is not FOSS -- the licensing terms mentioned above apply. #2 above requires users to license Spine and the Spine Runtimes license text to be included in the Product. #1 above requires that you have a valid license at the time of integration, that the Product add "significant and primary functionality to the Spine Runtimes", it defines distribution, has licensing requirements if the Product is modified, etc. Please see both license texts for full details. We have tried to make it short, clear, and easy to read, though legal stuff is never fun.
terry-kk I want to promote and sell this special Spine runtime as a commodity to obtain commercial profits
You can do this with either #1 or #2. Again the legal text is the authority and overrides any advice we give here. With #1, if 3rd parties (eg your customers) modify the Product containing the Spine Runtimes, they need a Spine license. With #2, all of your customers need a Spine license and the Spine Runtimes license text must be provided to them. In either case, someone using your Product probably has a Spine license, so I don't think it should be an issue.
The intent with all this is that we put significant effort into building and maintaining our Spine Runtimes and we intend them to be used by Spine licensees. For example, we would not like to see a competitor export to our formats and leverage our Spine Runtimes. Thankfully Spine has no real competitors, so this is only a theoretical worry. 🙂
terry-kk I achieved this goal on a platform with limited memory and performance resources and without 3D GPU. Moreover, the final rendering performance is also within an acceptable range.
This sounds cool! You could sell it as a web service or as self hosted software, or both.
