There are three main languages in the Enclave: in order of importance, they are Common, Dwarvish, and Orcish. All three are spoken and written.
Common is spoken and written fluently by almost everyone except a few reclusive dwarves.
Orcish is most commonly spoken by half-orcs (sometimes as a point of pride), but there are some of every race who have taken an interest in it. The grammar is simpler and the vocabulary smaller than Common or Dwarvish. Orcish as written by Enclave residents tends to be very simple and is not in widespread use. People who have encountered orcs outside the Enclave (and lived to tell the tale) report that 'Enclave Orcish' is somewhat different than 'Outside Orcish', but they are mutually intelligible.
All three of these languages have rich cultural lives in Enclave society, including abundant stories and songs. There are many written works in both Common and Dwarvish on a very wide variety of topics in the Magical Library. The Magical Library has several ancient books in Orcish, but they differ from Orcish as used in the Enclave, so they are difficult to understand. Few books have been written in Orcish by Enclave residents.
The Magical Library also has some ancient books and scrolls in other languages. Some of these resemble Common or Dwarvish and are somewhat intelligible. Others use completely different words/pictographs/scripts, and nobody knows what they mean.