Hey, I'm happy to hear that you're interested.
It's our 1st IO Game Jam, and we're still learning. To answer your questions:
1. As long as your game runs in a browser, it's fine.
2. For this jam, I'll leave it to our judges to determine whether it's a fair entry or not.
3. Open-source isn't required. However, I get the feeling that the judges will appreciate open source submissions more.
What are your thoughts? I'd love to hear your feedback on this.