What are the pros and cons of being happy at the rebirth of TGO?
Happiness in general is good for one's health, regardless of the cause of that feeling.
In this specific case you can be happy that something you once enjoyed and supported is doing well, despite its recent unfortunate history.
Perhaps you want to still be angry, and you want to harbour resentment, and you want to carry this emotional burden with you (all despite the extreme unlikeliness that eventual retroactive changes will make it all go away).
If you feel truly happy about something, you won't be capable of feeling this resentment at the same time.
So if you truly do want to feel anger, you won't be able to.
What are the pros and cons of continuing to abandon TGO as a matter of principle?
If you stand up for your principles, you can take satisfaction knowing that you are willing to sacrifice personal happiness and reason for a higher cause.
If you stand up for your principles, you are the only one that will ever know or care about it.
You will deprive yourself of the current and future TGO, and will deprive others of your new contributions.
If you abandon your principles, the only other people that will know about it are people that either already abandoned their own principles or never stood up for that principle in the first place.
Either way, it might matter a lot to you, but in general no one else cares about your choices.
(I don't say that in an insulting way, only as a matter of fact.)
I'm reminded of a barn on the outskirts of our city that had "Stop the City" painted on it, to protest urban sprawl. A few years later, when it was surrounded by little boxes, "All right, so don't" appeared before that message.