i know this topic has some time already but just wanted to give my contribution in a secondary solution, and maybe even easyer.
if you know any software that allows fullscreen ingame browser, download it and use it. then go to
www.kiwiirc.com and login to twitch chat. kiwiirc is a free web based irc client, i have used it for some time after i research a bit of twitch ingame chat and considered this solution a viable one.
browser window may be a litle bit larger than you could wish, compared to a solution where only chat letters would show layered, but still its resizable and software can allow transparency for it also.
i am using OVERWOLF (
www.overwolf.com) software for it, not only i use it to get browser running ingame with twitch chat, but it also gives
full control over teamspeak3 and for gaming people that is a big help also to have overlayed ingame.
it does also have a irc client plugin, however it has a huge publicity banner from mibbit (the irc client powering the widget) and it just ocupies too much of the widget window, making it harder to resize than browser window, and kiwiirc.com doesnt have big advertizments to crumble the window.
overwolf also has lots of usefull widgets, such as conection to most common IM services (gtalk, msn, yahoo, skype, facebook chat and others) but can also be used to record some video and screenshots, and software is partnered with teamspeak in a way that not only it gives full teamspeak controll ingame, but teamspeak client has built-in options to work with overwolf as well. on other words, teamspeak sort of made this software an ''official'' tool for gamers.
and thats about it, im advertizing too much already, but anyone willing to try this option, i believe they wont regret. and if browser window gets in the way of something, you can allways drag it around the game to a better position and scale it at your will, and also set transparency.