I didn't look indepth into this but the status field in the ost_ticket table is an enum. So if you were to open the database (with say MySQL Admin or MySQL WorkBench and edit the enum to be whatever you want it would change the Datatype for the 'status' column.
the default is:
ENUM('open','closed')
You would then probably have to go through most of the source code and change any instance in queries etc from 'open' to whatever you wanted it to say.
Which honestly sounds like a major pain in the *** just to change one little word. I don't think that I would bother, but if you do... good luck.