Hi Earl.
Today is my first look at e-Budo in several weeks.
I would like to suggest that before attempting to define "koryu" it is useful, first, to distinguish modern from premodern. Otherwise, one risks comparing and contrasting apples and oranges.
ONE: modern vs. premodern
Historians of Western sports and games have debated this distinction at length. Allen Guttman (1978, From Ritual to Record; 1994, Games and Empires) has his critics, but most discussions use his "family-of-characteristics" definition as a starting point. According to Guttman "modern" athletic endevors are characterized by:
1. secularism: not related to an explict transcendental realm
2. equality of opportunity: no one is excluded from participation on the basis of race or ethnicity; rules are the same for all participants
3. bureaucratization: not governed by priests nor by ritual adepts, but by national and transnational bureaucracies with defined institutional structures, committees, bylaws, newsletters, etc.
4. specialization: tasks are very specific and evolved from earlier less differentiated endevors; many participants have a gamut of specialized roles or positions
5. rationalization: rules undergo frequent revision to improve the practice; athletes train scientifically (based on emperical methods) and use technologically advanced equipment; safety and hygiene are stressed; there exist published textbooks and public training facilities
6. quantification: statistics are recorded
7. quest for records: best performances are recorded and there is a constant challenge for all others to strive to surpass them
To the above, I would add: (8) when competition is involved, there are standarized proceedures for matches and trained judges who follow established methods for enforcing rules and determining success and failure.
While Tokugawa-period kyujutsu certainly involved competition, statistics, and attempts to beat records, it did not possessed a majority of the above characteristics. Therefore, I would conclude that Tokugawa-period kyujutsu was NOT a modern martial art.
But is non-modern (premodern) the same as Koryu? Not neccessarily. In the 1830s many Domain Academies eliminated koryu from their martial art training halls and began teaching generic martial arts.
TWO: Koryu (old lineages)
This is a modern word invented to distinquish traditional martial arts from modern ones. Therefore, we naturally assume that the first characteristic of koryu would be a lack of a majority of the "modern" characteristics listed above. The word itself, however, does not explicitly imply the concept of "non-modern."
There is no deep significance to the word "koryu" (old lineages)---although, of course, practitioners of koryu can attach their own special meanings to it. "Old" basically means that the lineage existed before 1868. "Lineage" basically means that an identifiable connection united each subsequent generation with its preceeding one. Usually this connection would consist of: ryugi, mokuroku, and kata. The general assumption in Japanese martial art scholarship is that every koryu possess its own unique techniques and teachings (ryugi) which are conveyed through its own unique curriculum (mokuroku) and taught in as its own unique set of pattern practices (kata). As long as those teachings, curriculum, and patterns are taught faithfully from one generation to the next, then the lineage is maintained. In practice various documents (densho) usually are used to authenticate the transmission of the ryugi, mokuroku, and kata. Study of these documents from many different lineages (ryuha) reveals that teachings and practices always evolved over time as new elements were added and old ones eliminated. Moreover, there seems to have been a great deal of borrowing and cross-fertilization among ryuha. For this reason "lineage" is always a social construction imposed on the past. (In other words, it is something that can be debated in public forums such as this one.)
Best wishes,