Can I go out with his friend?

[Jennaholt]

Let's call my friend A. A and I met on tinder last year and our relationship started off romantically but it was mostly physical after that. And then we decided to be friends. Our friendship is slightly tense at times, given how we started off. We never dated but I guess there could be something more than just friendship. I have always liked him but for a few reasons, I knew things wouldn't work out between us. And around the same time, he started having a crush on someone. And they're dating now. I'm friends with this girl as well, he really wanted us to get along. Things are great on the outside.

I'm not sure how A feels about me. When we meet few months ago, he said "we'll see where things go between us." But after that, we hadn't been talking much over the past few months (as we were both busy). We caught up at a party last weekend. And I told him that it's been a difficult few months and that I had a really bad phase, distanced myself from everyone and didn't feel like talking to anyone. He asked me "anyone?" twice. He seemed pretty offended when I said yes, anyone.
I don't understand why he'd be offended as we did kind of drift apart after our fling ended, and our friendship after that wasn't something of "best friends." It was more of a "let's catch up when we're free" kinda friendship. Not too much effort.
I had also severely bruised my arm a while back. I guess a lot of people confused it for a hickey. A noticed it but didn't ask me until we got time alone and he went really quiet when he asked me. And when I said it was a bruise, he was like are you sure, and didn't seem like he wanted to know more about it. All this was weird because he doesn't wait until we're alone to talk about things.
I also noticed him looking at me at the party when I was talking to his best friend and we were all drunk so we were kind of hugging but it couldn't have been more casual. A had this lingering look on his face, I'm not sure what that meant.

Anyway, another one of A's (not so close) friends hit me up few days ago and we'd been texting. This guy asked me out on a date. I'm not sure if I should ask A if it's okay or not. I don't want him to think I'm asking to see how he reacts or make him jealous or something. But I also don't wanna do something that makes him feel uncomfortable.

[Rivière]

Based on what you've written, it comes across like A is a little jealous that you're moving forward, and past him. Given that he moved on and has started seeing somebody else, he may not have expected you to do the same and expected you to be pining after him. Perhaps he didn't know how to take the situation and liked receiving attention from you, regardless of how little it may have been. Of course this is all speculation and may not necessarily be true.

If A wanted to keep you as a close friend, or even just a friend in general, he'd have put more effort in. Not just talk to you/show signs of interest now that you've been taken off the 'I'm available' shelf.

Personally, I don't see why you should ask A if it's ok if you should go on a date with his friend. You're all consenting adults. You don't need A's permission just because the person you're going on a date with happens to be one of his friends, and a not-so-close one at that. Even though you don't want to make him uncomfortable, you're not A's property. You're not anybody's property. You shouldn't have to be asking anybody if something is/isn't ok to do. If you want to go on a date with this guy, do it, and enjoy doing it.

[Jennaholt]

Hey, thank you for the response!

One of the reasons A and I ended what he had is because he said he wanted a friend in me, and that we were only being sexual. We couldn't have both at the time, we would inevitably end up making out. While I liked him, it was more of a sexual attraction from his side. He told me that he hopes I'd be comfortable enough to tell him if I meet someone I like and that he hopes I do meet someone I like. I did mention that I liked him once way long back but I don't know if he remembered that.

Knowing him, he'd want me to be happy. It was his idea that I go out and meet other people. He practically dragged me to the party so I don't understand why he would be jealous. Unless he didn't expect to feel that way.

I don't blame A for not putting in effort, as I didn't either. We talked about this. We couldn't finish the conversation but we decided to talk about it soon.

I thought I should talk to him about it, because I wouldn't be comfortable with him seeing my friends. And even if he were to, I'm sure he'd check in with me beforehand. I also feel this is the case with anyone I know. I don't want things to get weird between us because we do care about each other and how the other person feels.