Where did the idea for a TDB come from? While in college, there was an experiment with a TDB using student body funds. Everyone was allowed to direct their $20 of student body funds to various student organizations. It didn't work because there was no guidance or leadership to this democratic budgeting process. One group on campus had everyone in their 'caucus' put the whole $20 in the group's name. As a result, that group became a dominant user of student funds and many other good and worthy activities received little or no funding.
There was no check and balance to this budgeting system. It was highly democratic, but it had no republican principles. One might point to our current republican based political system being the opposite extreme where individuals have very little in budgeting matters. The power is controlled by special interest collectives of one sort or another. Please note that democratic and republican in this context are small d, small r concepts and are not to be confused with the political parties that use these labels for their identity.
Our current budget system is controlled primarily by the politicos and special interests. The politicians take the revenue and after careful analysis, decide how to disperse the revenue to gain either the most votes or the most political contributions of various special interests. While some believe the resulting budget is representative of the ideals of the individual citizen of our nation as represented by these various special interests, such is hardly the case.
This is perhaps the crux of the TDB issue. Why haven't politicians ever asked the average individual taxpaying citizen where they would like to see their tax dollars go? What are the politicians afraid of? At times, contemporary politics seems driven by polling data of one sort or another. Is is possible that politicians don't want to put all of the budget questions into one single poll because such a poll would eliminate their ability to play special interests against each other for the most political gain and the greatest fiscal deficit?
The TDB defined in the home page is a carefully balanced system that takes into account the observations of the failures of these two extremes. Both democracy and republicanism are enhanced by the TDB process rather than both being compromised. Everyone turns out as winners.
Everyone who desires to, can participate (the democratic part). However, the elected officials of our republic control the basic guidelines for the budget so that some basic budget realities and guidelines, such as payment of interest on the debt and a proper defense while promoting the general welfare is provided for (the republican part).