Be careful of SuperKaramba, it is addictive. Today I noticed, what a good example SuperKaramba is for the great pleasure of OpenSource development. I watched this process over and over again, now. You just have some ideas, some slices of imagination coming up in your head. Then you're going to write them down, either as headwords or by actually starting software development. Some rules to guide you to a happy developer.
First rule: Release early and often. People will take up your ideas, improving them, giving you feedback. Sometimes it's helpful enough just to get a good tip by some old, long-bearded guy, which will keep you on the track and in the right direction. Bugs could be found quickly, since everyone's able to track even the "un-reproducable" errors down to their source-code line.
Second advice: Keep a clean coding style, close to some known standard. Comments are important, too, since others will have a chance to find a good entry point for their development. Just think off yourself looking for the start of a change at some other's source code. You'd be thankful for nice comments.
Use standards and accepted interface types, don't create own ones. There's an exception in my eyes: If you're going to create a static client/server system, I'd prefer self-defined protocols, which are traffic-savvy and adapted to the project's purpose.
Last point: Why do all the work by yourself, if there are so many people interested to help you? Just start the project, just do the start-off. Wait, release and annouce, and others will soon help you, bringing new thoughts to the project, helping you gaining more freetime.