I'm the person who originally asked this question on a different forum.
Many thanks to HonoredShadow for reposting my question on this board.
We have since found the answer:-
Although previous versions of this game had to be registered, it now appears that the freely downlaodable release of version 6 has the limit removed.
It says in the readme.
Sure enough I've been playing this for a day or so now, and the limit is no more.
Hope That Helps,