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Latino sine flexione is a variant of Latin created by Peano in 1903. As far as I know it was used in scientific literature but since forgotten.

I found this site and a few discussions on Duolingo but not a single speaker.

A quite complete grammar can be found here.

Is this wonderful project dead?

It seems the original project evolved into what is now called Interlingua. The Oxford Essential Dictionary of Foreign Terms in English defines Latino Sine Flexione as:

The language Interlingua, in which nouns are taken from the ablative case of Latin nouns.

Meanwhile, the Encyclopedia Britannica states:

Interlingua, also called Latino Sine Flexione, simplified form of Latin intended for use as an international second language. Interlingua was originally developed in 1903 by the Italian mathematician Giuseppe Peano, but lack of clarity as to what parts of Latin were to be retained and what were to be discarded led to numerous “dialects” of Interlingua, confusion, and its dying out among enthusiasts. In the late 1940s and early 1950s, the linguist Alexander Gode, with the sponsorship of the International Auxiliary Language Association, reformulated and revived Interlingua and promoted its use in the international scientific community. As reformulated, Interlingua’s grammar is not much more complex than that of Esperanto; it has only one form for nouns (taken from the Latin ablative case), no gender, no case, plurals in -s, one form for adjectives with no noun-adjective agreement, one definite article, and verbs with no inflection for person or number. Abstracts and summaries are published in Interlingua by several international scientific journals, but in general the language has not been widely adopted.

Wikipedia, on the entry of Interlingua, says:

Today, interest in Interlingua has expanded from the scientific community to the general public. Individuals, governments, and private companies use Interlingua for learning and instruction, travel, online publishing, and communication across language barriers. Interlingua is promoted internationally by the Union Mundial pro Interlingua. Periodicals and books are produced by many national organizations, such as the Societate American pro Interlingua, the Svenska Sällskapet för Interlingua, and the Union Brazilian pro Interlingua. ...

Interlingua has active speakers on all continents, especially in South America and in Eastern and Northern Europe, most notably Scandinavia; also in Russia and Ukraine. There are copious Interlingua web pages, including editions of Wikipedia and Wiktionary, and a number of periodicals, including Panorama in Interlingua from the Union Mundial pro Interlingua (UMI) and magazines of the national societies allied with it. There are several active mailing lists, and Interlingua is also in use in certain Usenet newsgroups, particularly in the europa.* hierarchy. Interlingua is presented on CDs, radio, and television.

Interlingua is taught in many high schools and universities, sometimes as a means of teaching other languages quickly, presenting interlinguistics, or introducing the international vocabulary. The University of Granada in Spain, for example, offers an Interlingua course in collaboration with the Centro de Formación Continua.

Every two years, the UMI organizes an international conference in a different country. In the year between, the Scandinavian Interlingua societies co-organize a conference in Sweden. National organizations such as the Union Brazilian pro Interlingua also organize regular conferences.

Out of curiosity, yet there seems to be no Unix OS, Mac OS, nor Windows OS supporting Interlingua.