An answer can be either simple or complicated.

The **simple** interpretation is: Marx was trying to describe the ethnical makeup of the _complete_ population of Jerusalem. So, when he writes about "Mussulmans...consisting of Turks, Arabs and Moors", the Moors must be all Muslims that are neither Turks nor Arabs.

The **complicated** way to interpret the text has to take into account that for Karl Marx, English (the original language of the text) was a foreign language, and one he learned (to my knowledge) only as an adult (in contrast to German, his mother toungue and French, learned as a schoolchild). It is known that until 1853 he employed Wilhelm Pieper as a private secretary and for English translations. Whether he still used the help of a translator in 1854 is unclear to me, it seems that these "private" translations have not been documented. Anyway, it is possible that he thought of a German term before the English one was written down for the manuscript sent to the Herald.

That gives a bit of a problem, as there are two German words that are based on the originally spanish "moro".

- [Maure](https://de.wikipedia.org/wiki/Mauren) is and was mostly used to describe the Muslims of el-Andalus and northwestern Africa (Berbers). It is the closest one to the English use of "Moor".

- [Mohr](https://de.wikipedia.org/wiki/Mohr) has been a term that was used in multiple ways across the centuries. Its most colloquial usage since middle ages designates a person with dark skin, and it was used to translate the greek _aithiops_, burned skin. Martin Luther consequently used the term "Mohrenland" for Ethiopia, and until the 19th century there is a tradition to use it specifically for people from northeastern Africa (Ethiopia, Somalia, Abessinia, Eritrea, Nubia), while others used it for all sub-saharan Africans. At the time of Marx, the term "Neger" had become much more common, based on the contemporary theories of "race". "Mohr" started to become an outdated, literary or [heraldic](https://en.wikipedia.org/wiki/Moor%27s_head) term. Today it is considered to be stereotypical and degrading. If pronounced the German way, "Moor" and "Mohr" sound the same.

The re-translation into German for [Marx-Engels-Werke](http://www.mlwerke.de/me/me10/me10_168.htm) uses the term "Maure". But since this edition is not based on historical-critical methodology, that is only a weak hint. The detailed circumstances of the word usage could possibly be found in [MEGA](https://en.wikipedia.org/wiki/Marx-Engels-Gesamtausgabe), which I don't have available.