The master branch currently tracks Sage 10 which is in active development. Looking for Sage 9? See releases.
Sage 9 is essentially “complete” in the sense that we aren’t actively working on it: We’ll consider PRs but unless some horrifying security flaw is discovered it won’t see active development again. Because it’s no longer under active development, you may see some level of “dependency rot” as time passes–there are several topics in this forum with people working through issues of that nature.
Sage 10 is still an in-progress, unreleased product. You can use it if you want to (I have, on several sites currently in production) but you should only do so if you are comfortable solving your own problems. While plenty of folks here will probably be happy to help you, Sage 10 is still potentially in flux and if things change enough it will be difficult for other people to debug your problems.
So essentially, as long as I can solve issues with Sage 10, I should be fine. If you do update Sage 10, I can always possibly update the code, to the new one, right?
So it seems Sage 9 is more of a possibly stable version, but Sage 10 should be out soon-ish? I think its been over a year now that Sage 10 has been under development if I remember. I think with Sage 9 I found quite a few issues, in general it kinda looks unfinished in some parts, but It is what it is.
I think Sage 10 should be fine, because I can always ask help here, and in worst case, pay someone, say a senior dev that does PHP/WP to help me solve an issue.
Well, am going to build my system around Sage 10, worst case scenario default to normal WP xd
Is there a funding page where people could donate for the development of Sage? This is how WP should have been built.