Legalities of Reimplementing Proprietary Languages?

Morgoth_Bauglir writes "I have written a syntax checker for a proprietary language that my company uses for our core business operations. I believe that my syntax checker can be extended to be a full-blown re-implementation of the language. This would be useful, because the gigantic company from which we license that language is continually "improving" it and then not supporting the older versions, which requires increasingly expensive upgrades. Increasingly expensive because the small company I work for has moved into direct competition with the software provider. There is the danger that the language will be priced out of our reach, requiring us to seek a different solution."

"I built the syntax checker based on their language specification, I have not attempted to reverse engineer their interpreter (it's broken in a couple of ways anyway). I think there is a copyright on the language specification. Does this mean I cannot implement the language?

Would a re-creation of their language be legal? I haven't ever seen their source code, nor has anyone at my company. I do not intend to redistribute it, only use the interpreter in-house so we can continue to use our old programs without paying licenses. We had to write those programs, so to the best of my knowledge, we own them (but not the language they use?).

Or, would a re-implementation be, in effect, the same as making multiple unlicensed copies of their interpreter?

If I cannot implement the language without permission, does this also mean that I cannot create a converter to translate that language into a different one? Could such a converter be construed to be an implementation of the language?"