It's not needed for true ending. But nothing bad will happen even if you've seen it.
Thanks man, I just completed the True Ending, one of the best games I've played I gotta say, I understand why you chose to translate this and I'm very grateful you did! I actually found this thread/game because I was looking into the other game you translated (by Odensensei) and I was looking to see if the translator had translated any other similiar works, so that was quite a lucky find lol.
Here's some free QA of stuff that's fresh in my mind if you want it:
There's some untranslated stuff left in the game scattered all over, the ones I still remember are the morning after event after you spend the night in the male toilet in the park, the command to get up from water (after any swim), the obscure long book (to skip days), the entire conversation with the Otaku when he opens the secret vault in the library, a lot of NPCs in the bar (where you go with the principal).
There's a lot of lines that goes outside the text box but it's totally understandable since it's not the final release and this is the kind of thing you'll notice when you proof read/play it.
There's way too many japanese words used as intentional non-translations in my opinion. I know what "kami-sama", "miko", "nee", etc means because I've dabbled in japanese culture but to the majority of people I believe this will be a very hard translation to understand since so many japanese words are untranslated or treated as a specific name/thing, the three things I mentioned earlier could've easily just been translated as God, priestess and sis/sister and it wouldn't have made it any worse in my opinion. And those three examples were just some of the easiest, and most easy to accept, but take a look at just this one comment for example (spoilers):
stuff like that I think will almost not make sense to most people. Either find a fitting translation or give a good explaination what the word means (although this can be borked by the order of when the word first appears). This was only supposed to be a minor gripe but it ended up taking such a big portion of the post, lol, sorry about that.
Don't take it as being critical though, this is just a casual enthusiast sharing his views, this was a 10/10 game and 10/10 translation!