I do not know if he is stealing or using any of your proprietary content for personal gain. I can say that he has written a very nice tool that offers a much needed service.
Even though I tried using your Unity support software, it did not compete with this tool. Spine is an awesome 2D animation utility, but your Unity support is basic at the most. There were many problems using your support tools, and if you go back through the forum you can see that is h has been quite buggy. This tool has just worked with no problems, and has more features, which IMHO are greatly needed.
As previously mentioned your tool is lacking. I am sorry that I mentioned this asset to you because I really would hate to see it go away. On the other hand how can accuse this person of stealing? And do you not have to prove to Unity that this person is stealing and not just accuse them. Now if the person is stealing that's one thing but please check this out thoroughly for not only all the people that have already purchased the asset but for those that will in the future. This asset is making it easier for people to use Spine animations in Unity.
And if it is found out that this person is stealing then hopefully you can create a tool that is just as good or better.
Also, though it is irrelevant now because of the asset that I am using instead of yours, but you still have not answered my question about why is the "Animation Import Type" option not available?