You can make boards bigger than the licensed maximum for your version
of Eagle, and you can make boards that extend into negative X and Y
territory, it seems.
Regarding the licensed maximum, it seems the limitation applies only
to placing devices from libraries. The limitation does not seem to
apply to dimension lines, traces, holes, text, or anything else that
does not come from placing a device from a library. And if your
library device hangs out over the licensed boundary, that is OK too,
as long as the center of the device is in bounds. This can be useful
if the active circuitry area of your board is within legal bounds, but
you would like to enlarge the board just for the purposes of providing
mountings.
Regarding placing things (not library devices) in the negative X or Y
territory, Eagle handles that very nicely too. It figures out a
proper X and Y offset when the CAM processor makes Gerbers and drill
files. All the Gerber and drill file coordinates come out positive.
Nice to know.
Robert Scott
Real-Time Specialties
Ypsilanti, Michigan