They also want half the business, despite the fact that I'm the one doing all the work, pulling the long nights of coding in.No, you aren't, not if you're planning to build a real business out of it. In addition to simply having "the idea" somebody has to talk to customers, solicit feedback, do market research, evaluate and establish pricing, develop a marketing strategy, write datasheets, whitepapers, blog entries, press-releases, etc., somebody has to talk to journalists and manage PR, somebody has to track down and woo investors (if you decide to seek outside money), somebody has to sell the damn thing to somebody, somebody has to do the legwork of tracking down partners, resellers, and possible "joint venture" participants, somebody has to file the legal paperwork to create a legal entity for your venture, open a bank account, get a DUNS number, get a EIN number, etc., and etc., etc., etc...
No, the programmer really is not doing "all the work". NOW, it may be the case that the erstwhile partner who is wanting to work with you can't (or won't) do all of the things listed above. Fine, in that case, if they can't code and they aren't putting in any money, don't work with them. But you should probably know whether or not they are a coder, or a legitimate "business person" (as opposed to "Just an idea guy") before you spend any substantial time working with them in the first place. These are questions to ask up front.
Keep in mind though, that the non-coder has plenty of value to bring to the table (and if they don't provide any of these things, walk away): connections with customers, connections with investors, deep domain expertise, marketing / positioning / biz development knowledge, sales closing ability, etc., etc.
- Does anyone else have this problem?
I don't think the problem you are describing even exists, as such. The whole premise seems rooted in a lack of awareness of the importance of all the "other stuff" besides coding that goes into building a business.
- How did you deal with it?
See above. I'm a developer who has forced himself to walk on the "business side of the fence" the past few years exactly because we don't have that "business guy" to lean on. So I'm not just talking out my ass here... I've learned first hand, this stuff is fracking hard and is easily just as much work as the coding and is just as important.
- Is it illegal to just "walk off" with someone's idea?
Depends on a lot of details, most likely. But it's somewhat of a dick move, whether it's legal or not.