Hi Dmitry,
I am happy you mentioned this and are willing to take steps toward a solution. Seems like many programs are out there (some VERY good), but none of them coincides with Allen's GTD system as if it were built specifically for it.
I am C# programmer as well and would 2nd your vote on using it; this would be a great language for the project. I also agree the application written for the windows platform would take care of a large percentage of users; however, as you stated, would leave a minority (yet still large enough worthy of attention) of non-Windows users out in the cold and a bit salty. This would be a strong point of a web version that would be compatible with non-Microsoft browsers.
Concerning joining the project, I personally have never had good luck working side-by-side (outside the boudaries of being co-workers at the same company -- not independent) in this manner, even with the closest friends or family members.
In a project like this, the experienced developers tend be quite passionate about their vision, their design, and their coding style which is almost dear to their heart as their religion. The phrase "too many chefs in the kitchen" or "too many chiefs and not enough indians" comes to mind.
I hope you or some one would be the central, "in charge" developer/architect who would have to make the final call on some tough decisions on the way things are done or set up.
Then there's also the issue of one developer doing most of the work or "making it happen" or taking responsibilities of the gray area (or he/she just perceives it this way) and splinter groups of developers taking the code to do it "the right way" saying it was theirs since they "did all or most of the work". You may get a few programmers on the project who aren't seasoned. You may need to decide how to handle rewriting their portion while he/she is seeking legal cousel for nonpayment and you have to prove what he turned in was unacceptable. :-(
I'm not sure if you planned on creating a business entity out of this or not, but I would feel very uncomfortable opening myself up to what other partners decide on or commit to without my accord. I've heard many horror stories on partnerships, and I hope you protect your investment of time and resources legally.
Currently my mind is on a web based version of this software; and it seems your heart is set on the windows platorm. I would be willing to form a mutual beneficail information exchange on specifications and file formats.
This type of collaboration would end up being a win/win for us and the users, without the need to split any profits. This would allow all of our software (more developers may need to step up for developing the PocketPC and the Palm versions....and don't forget about Mac, unix, etc. platforms) to work well together so everyone is "Getting Things Done".
For an example, I could expose all the user's data through web services (for importing and exporting) on the web server which you could call from a windows based machine and sync it up with Outlook. I would assume all forms of these programs would track the same types of things such as projects, action items, etc. What do you think?
If you guys plan to write a web version in the next few weeks, I'd hold off to use yours. I'd much rather pay for software than have to write it from scratch. I just want to be "black belt" in GTD-do Karate ASAP ;-)
Happy Coding!
