I helped build Chat Simply: https://www.chatsimply.com https://www.chatsimply.com it is XMPP backed, has Windows and Mac OS client as well as iOS. It is also we

I helped build Chat Simply: https://www.chatsimply.com https://www.chatsimply.com it is XMPP backed, has Windows and Mac OS client as well as iOS. It is also web-based so you can use it in your browser if you would like. It is free but has some "Pro" features for a reasonable yearly fee. BTW we officially launched it today, so this is good timing :)