Actually you still have to use a windows client to report taxes here in Ecuador. Any way i know people from SRI who wants to migrate the system to java so it would be multiplataform and hopefully make it free.
The good thing about the way you report taxes is that there is an open format made with xml so in theory anyone could make and application for this and make it free software. This hasn't happend yet.
Anyway there are a lot of things goin on in Ecuador in favor of free software and that is thanks to free software activists in our community.