the Robot Invaders contest presents you with 3 3rd party SDKs to use for building your bots. the summary page doesn't tell you much, and i'm assuming you don't want to do a trade study, so i'll give you a quick rundown.
the simplest SDK is Incesoft. They seem to be a Chinese company, so the forums and docs are a bit choppy ... but still easy to understand. their SDK download is about 200K and the docs are 13 pages. you have to do some setup on their website which isn't too bad either. their servers are used to handle your bots presence, and your app connects to their server. the website allows you to change the bots name, picture, personal message, and add custom emoticons. it comes with a .NET sample that is really easy to understand. in the code you'll be writing, you can send nudges, open web pages in the Activity window, change the dialog preface, and send messages of course. to do more advanced stuff, you need their Enterprise solution ... which costs money. the enterprise version supports multi users, winks, voice clips, shared background, and file transfer. its lame that we only get partial access to MSN functionality for free. anyway, this is the lightest SDK that you should be able to get setup and running the quickest; it's what i used for my 1st bot.
another SDK is by Conversagent. their shining example is the Encarta agent. their SDK is about 40 megs to download and the docs are 385 pages. the SDK installs an IDE which is primarily used for dealing with BuddyScript. BuddyScript is a text format for specifying dialogue. e.g. if the user says 'what time is it', then the correct script will be run to determine the time and return a response to the user. i.e. BuddyScript is like AIML for the AliceBot. if your bot needs to have alot of conversation, then you'll probably choose this option. but if you want to code in C# ... then you won't find any mention of it in their 385 page SDK. so if you don't need BuddyScript for your bot, then i don't see where to point you. personally, i don't want another IDE or to learn some proprietary script language. what is really good about this SDK is they support VoiceClips, winks, backgrounds, contact cards, etc... for free.
the last SDK is the L7 Builder by Akonix. their SDK is 104 megs and they have multiple docs. they do have a doc specifically for developing with .NET and C#. the code might be slightly more complex than Incesoft's, but it also looks like you get some more functionality too. the bad news is their Administrative docs are larger than their developer docs. serious, adminstration looks more complicated than it should be. and the installation had a bunch of crap in it ... including Apache. er, um ... i really don't want to install another web server on my dev machine. and why in the world do i need a web server to develop a bot? what i do really like about these guys is that VoiceXml is an option. but not for doing speech reco and synthesis, just for handling the dialog. speech development is all about having a dialog with the user, and that is what VoiceXml is designed for. to me, it makes much more sense to use VoiceXml (or SALT) instead of BuddyScript. plus there are standardized XML formats for specifying grammars in the speech world.
so that's my quick trade study. their are advantages and disadvantages to each, so it really depends on what you want your bot to do. Incesoft needs to add funcionality while remaining lightweight and simple. Conversagent needs to get me closer to code and make BuddyScript an option, plus lose the IDE. Akonix needs to lose the huge install and simplify administration. but i still can't figure out why MS doesn't have their own bot SDK? they could definitely provide something as lightweight as Incesoft's, while exposing all the features for free. when it comes down to it, it's just about implementing the MSN protocol ... how hard can that be? plus, i would take it more seriously that they want to support bots on MSN.