Nepal bhasa (also commonly known as "Newari", but it seems this term has been introduced by foreign scholars and is not fully accepted by a lot of Newah people) is a Tibeto-Burman language spoken by the Newah (also known as "Newar") people who are the original inhabitants of the Kathmandu valley. As of today, there are still about 800,000 native speakers who use it daily as their mother tongue.
Even though Newah bhay is a Tibeto-Burman language, a huge part of its lexicon has been heavily influenced by Sanskrit over the centuries. There are few good resources available to learn this language and the number of speakers seems to be decreasing every year. The new generations only use it at home with their family but practically never in other life situations : Nepali and English are used at school and at work.
Newah bhay used to have its own scripts in the past (Prachalit, Ranjana and a few others). Today, it is written in the Devanagari script most of the time. The Ranjana script is only found in Buddhist temples and only its decorative purpose has remained in use until today (most Buddhist "prayer wheels/mills" are carved with this script today, even in China, Japan, Korea etc.).
For those who have an interest in Himalayan languages, more detailed information about Newah bhay can be found here :http://www.omniglot.com/writing/ranjana.htmhttp://blog.shresthamanoj.com.np/2012/0 ... ewari.html
The only "textbook" available to study the language a bit more in depth is, to my knowledge, the one written by Sushila Manandhar, a Newah scholar currently teaching at the INALCO (French National School of Oriental languages, the French equivalent of the English SOAS). Unfortunately, it is only available in French. The Devanagari script is used throughout the book to transcribe Newah bhay :http://www.amazon.fr/Parlons-n%C3%A9war ... 2296107710
If you have an interest in Newah culture, please have a look at this website :http://www.jwajalapa.com/
नेवा: भाय् तसकं बाँला: भाय् खः |
(Newah bhay is a very beautiful language.)