Uhhh, screw that?

Unless you're in a country where the laws are abysmally bad, that shouldn't be an issue. In the USA, at least, it's a legal right to reverse engineer for compatibility purposes. Making a compatibility program/plugin for an unsupported platform sounds valid enough to me.

Legalities are a bit trickier if you publish the reverse engineered results in open-source program form, but my unprofessional opinion is that you're still legally in the right to do it... In the event that they decide to be a-holes and try to sue over that, you may well be able to enlist the help of the EFF (Electronic Frontier Foundation), who I believe volunteer their lawyers towards cases of significance towards protecting digital freedoms.