I have now commented out line 268 as suggested by Waffle, deleted the OneWire.o file to cause a recompile, and tested the revised code with seven devices. It works.
For those who might want to duplicate this fix, here is a print out of the area in question with the commented line in place.
263 } else { // we are blazing new tree, take the 0
264 a = 0;
265 searchJunction = i;
266 done = 0;
267 }
268 // lastJunction = i;
269 }
270 if ( a) address[ ibyte] |= ibit;
271 else address[ ibyte] &= ~ibit;