You should be able to build a desktop app that runs in the browser using web2py. Web2py requires no installation or configuration, has no dependencies, and includes a built-in web server and the SQLite RDBMS (as well as a database abstraction layer). The Windows and Mac binaries even include the Python interpreter, so no need to install Python (you can even run it off a thumb drive). You can pack your application with a web2py distribution, and your users will simply have to unzip it, click a single file to start it, and your app will launch in their browser. You can even distribute your applications as binaries, as explained here.
The documentation is excellent, and if you have any questions, there's a very helpful and responsive mailing list.
If you want to start playing with it, just download it, unzip it, and click the web2py.exe (Windows) or web2py.app (Mac) file -- that will launch the "welcome" (scaffolding) app in your browser. If there's something it's lacking that would be helpful for your use case, ask on the list -- if the change is easy and useful, it will probably get added.