As Lenco has pointed out, .mds is alcohol's native file format and, presumably, such rights as there are to the formay belong to them.
I don't know how or why LIGHTNING_UK! was able to use the format (presumably with Alcohol-Soft's permission). However, insofar as he had any rights to the format (as opposed to a mere permission terminable at will), those rights must have passed to the current owners of DVD Decrypter.
Sadly though, I have to point out that DVDD is not an abandoned work. It's current owner is Macrovision to which L_UK assigned all his rights to the program as part of his settlement with that company. [Needless to say though, since Macrovision owns all rights to DVDD, there will never be any further development.]