I'm very surprised that wwndata, as well as every similar mod, uses a fat client to upload a file to a website.
why don't you write a server-side application and a simple HTML form to upload the file to the website?
if you think asking a user to upload the file manually is too much trouble, then at least you can use the form/website as the back-end for a fat client that does a simple POST.
If you use the website to collect the data you have one client to maintain and then ya don't have to worry about Mac and Linux support - you support everyone equally.
I'd be happy to help with such a project.

Artemishka: Orcish Hunter of Dethecus, Human Software Engineer of Chicago