Now you guys make me curious! I know that I have a copy on Maple V R2 or even R3 lying around---on floppies, no less---maybe is should spend this weekend to dig it out & install it...?? But I certainly do not have any license numbers or keys for these anymore.
I do wonder, however, why you want to. As far as I can tell, the old packages (linalg etc.) are still around, if deprecated. I have downloaded quite a number of Maple V programs and code snippets from the net and so far have not run into any problems (this is with Maple 15). In those days I ran Mma so I don't have old Maple routines of myself.
One thing I would yearn for is to be able to use the older interface of Maple (I think they call that "classic"), Running on Mac's I do not have access to it. The Java interface we are made to use is in my view not quite up to it; being sluggish and having rendering issues. In addition it does not take full advantage of running in a separate thread: I find when the Maple kernel is busy the interface is mostly locked up. The only good thing I see is that, on a multicore machine, mserver can get 100% CPU on one core & let any GUI overhead run on the other one. I would run in CLI mode if it were not for the graphics output, which I would not want to miss; and I do not think Maple supports something like AquaTerm (graphics screen for CLI processes on Mac OS X).
Anyway, so far I thought Maple's backward compatibility to V is not bad.