The pilot reported that during rollout from a practice landing on runway 25L in his amateur-built, experimental biplane, he may have applied unequal toe brake pressure. The pilot stated that he lost directional control of the airplane, and while decelerating, it swerved about 60 degrees sideways from the runway's centerline. During the mishap, the right main landing gear collapsed under the fuselage, and the lower right wing impacted the runway. The pilot reported no mechanical failures with the airplane at the time of the accident. At the time, the surface wind was light and variable. A Federal Aviation Administration inspector examined the airplane. He reported observing that the outboard portion of the lower right wing's aft spar was cracked.