OK, more details.
I'm still forming ideas, so bear with me. I envision a M$ Project-like program (but not TOO like it, it sucks), but one that works. I want to reinvent how project management tools present data to the various stakeholders in software development projects. (yes, software projects are quite different than say building bridges, etc.) So, it would first be a sort of spreadsheet application. It will heavily use probabilities to give more realistic expectations for probabable outcomes; beta distributions actually model projects risks extremely well. Some standard project management tools are pretty much outdated (IMHO, and I've got a masters degree in project management), like PERT charts. The PERT data will always be useful, but the diagrams themselves are next to useless; the data could be conveyed in reports and other methods much more effectively, with the computer doing important things like recommending how to crash schedules.
I envision possible web interfaces to a database. Distributed programs (ala Beans), and connectivity to user defined databases for calendar, costing and other important data.
I envision data such as schedule variance and cost variance being made available at the project, task group and resource levels.
This is just a quick overview of my plans. I have lots of ideas, and lots of experience in how NOT to manage software projects.
I want to use as many open source tools as possible. That is one area of confusion for programming language. I want a fairly easy GUI development environment. I want a nice set of tools for displaying and graphing data, and writing reports. I want to be able to publish selected data to websites easily.
I consider C because it is proven and I know it well. I worry a bit because it may be going out of style and may not have the tool support going forward that I would like. I don't know C++, but I suppose I could learn it.
I consider Java because it's a lot like C (with classes), and that's good and bad news. I believe Java will be around for a while as it seems to be popular, therefore I expect that tools will remain available and will continue to be developed. Java is also a mostly platform independent language, which is a small plus. I'm not crazy about the startup time for larger java programs.
I would consider Kylix, but I hear development is stopping on it, and it may become unsupported. It also has poor database connectivity in the free version.
I would be happy to provide any other information. Just ask.
Thanks!