What platform were you thinking of getting started on?
As far as source code goes, I don't think you'll find any particular programmer/developer that has worked their tail off to spawn anything, willing to hand over a chunk of source code to help launch a potential competitor
But, whether you choose linux/unix or a windows platform to begin this adventure, there are certainly tools to help you along the way.
It just depends what environment you are looking at- to begin with.
Well first you have to circumvent the evils of IIS and tame it to your liking, but that's a part that many people have had documented (and microsoft actually makes it quite easy with IIS5/win2k).... there are plenty of ADSI books available at amazon.
But everything beyond IIS is the real question mark. But perhaps you don't need a panel for anything besides managing that- if that's the case, no worries. however-
The key for a breakthrough win2k panel is still something nobody in the industry has mastered yet. There are a few dozen people working on a win2k panel, be it for their internal use, or to distribute or sell.... if anyone decrees HostingController is the answer, then I'm sure you'll have another 200 people in your face within moments.