is it possible, i.e. so I can use my mach3 on a lappy in the garden

yes.

I believe it is unlimited use for the same user.

If you're machine is making you money, you need a license for each machine making money. If it's not running a machine, or running a machine as a hobby, you can use it on as many machines as you like.

I will use the machine to make money, however the planned h-bot corexy machine I want to make I think is unable to be run with a
h-bot non traditional cartisan mach3 g-code post processor I have looked and nobody seems to have written one.
I have bought the mega arduino and ramps 1.4 and the little lcd, but alas ther, there isn't a way of importing 2d graphics orientated files into marlin / sprinter.
so I am fackered either way = ha ha ha!!!
the future maybe bright though as seemingly IF that nice man just wrote the 3d printer hot end wizard for trad x-y gantries gantry's for mach3
then some bright spark will undoubtably write a h-bot co-ordinate system as IF the glue gun head already exists, surely someone can see the benefit of having an OPEN ENDED GANTRY  - so for example you could roll your large open ended cnc h-plot bot corexy gantry into position , then proceed to cnc place (or print) extruded lost wax / investment casting goo on the floor and then simply roll the cnc machine away.

or stuff like that.

IF you like it time to make them little machines a bit bigger . -I think so anyway.

I would like to cnc place (or print) letters for signage backward on the platen in reverse with bevelled edges/ side returns to then install strip led's into them, that can be powered by those little solar panels that can simply be clicked into the cnc placed (or printed) orifice - positioned to the top, then print the location studs too- really fast
I can dream can't I??

plus I want a plasma cutter h-bot so I can do similar to above but tig the returns but still have the solars atop - need to figure out how on a curved top letter though, you can't see the tops from the street !