Dialect here refers to different attempts to create of Orcish or Neo-Black Speech.There are several attempts to construct a neo-version of the Black Speech and Orcish but the distinction between Orcish and Black Speech is not always clear. As far as I understand it different people contributed in the early 90th and A. Appleyard (Appleyard) compiled this in 1994. This seems to form the base for the Swedish LARP dialect Svartiska which seems to have been created in in the early 90th and largely completetd by the end of the decade. The Middle Earth Role Play (MERP) made a list of several Orcish words not based on Tolkien material but incorporated in Svartiska. (I have the book “Angmar”, second edition 1995.) The Land of Shadow (LoS) dialect ( from 1998) is the most wide spread which share quite many features with the Horngoth dialect (grammar from 2003). See The Black Speech School for more information on the dialects. Then I have created the Zhâburi which is described on this site (Zhâburi A 2011 and Zhâburi B 2016 ongoing construction on this site). Then there is David Salo’s Black Speech and Orcish which he constructed for Peter Jackson’s movies .
Zhâburi is the newest attempt that I know of to create a Black Speech. The first version (A) is a variant of Svartiska but the second version (B) is more free standing but still connected to Svartiska but also LoS and Horngoth. See also my analysis of Black Speech and Orcish.
We know very little of the languages of the Shadow but one thing is certain there is a clear distinction between proper Black Speech and Orcish (here I elaborate on the relationship between Orcish and the Black Speech). As David Salo writes
Sauron, I imagined, was an enormously practical person, who would have made the Black Speech as “perfect” (according to his notions of perfection) as he could make it, with a rigorous consistency and logic, but without making any allowance for æsthetics. It would not eschew borrowings from other languages of Middle-earth, but it would adapt them to its own style. It would in fact have been, as my friend Helge Fauskanger terms it, Sauron’s Esperanto.
In sharp contrast to the relatively tight organization of Black Speech, the Orkish languages were to be simple, disorganized, and inconsistent, the result of years of rapid and ungoverned evolution. There would be grammar, of course, but also a fair amount of toleration of variation, and a continuous tendency to proliferate new words and abandon old ones. They would show a strong influence from Black Speech, at various stages in their development; but they would fail to adhere by its rules.
The Appleyard dialect have no clear distinction between Orcish and the Black Speech and draws inspiration from both the known Black Speech and the known Orcish but it is explicitly an attempt to construct a Black Speech. LoS is an attempt to construct a Black Speech. Svartiska, Horngoth, MERP and Salo’s are instead attempts to construct Orcish languages. Svartiska for example has many alternative grammatical rules and synonyms reflecting the different Orcish dialects.