From the "Version IV" introduction:
"These aren't the complete rules to Ysgarth. The minirules are the most basic version of the rules, with enough information to play a limited game of Ysgarth, but without some of the details and refinements. Complete mechanics can be found in the full version of the 6th edition rules."
A variety of these "minirules" documents were produced, typically distributed at game conventions or via the mails. They ranged from a single double-sided page to an eight-page folio pamphlet. The longer versions typically contained advertising materials as well as rules.
The game's designer, David Nalle, was also posting various iterations of the minirules online (as a plain text without art) as early as 1995.
The minirules appear to have been revised fairly often. Version 2.5 is dated 1993, Version 4 is dated 1994, Version 5.2 is dated 1995, and Version 6.7 is dated 1998. Nearly all of these documents appeared after the publication of the 6th Edition rules (in 1992).
Note the Version 6.1 and 6.7 documents contain minor rules errata, demonstrating the iterative development of a planned (but never published) 7th edition game.