Greetings, it seems that the git has gone 404 and there's seemingly nowhere to get old versions of the viewer.
I require the viewer for version 2.5 and 3.1, the viewer is useful as a fast way of checking that your animations are working well when you cannot work on current version plus it's often useful to send it to programmers so they don't have to install spine trial and you having to send them source files so they can see what they are working with.