Ah, well, then you're fucked. My point is not that you should consider it a good idea to make your own proprietary language, just that that situation can sometimes be a really good, productive one.
(I'm dealing with this in my work -- we use a proprietary internal scripting language, and the guy who wrote it is not around. I'm slowly becoming the local expert on the language -- very slowly, though, because opportunities to work on it don't come up too often.)
