What are the practical benefits of this library?
We have gtk,qt,fltk,wx, and a long list of others some cross platform some not..
2. Cosmoe is under the MIT license, which may be of interest for those wanting pure MIT/BSD-licensed solutions, as well as for those who want to use a C++-native toolkit but are concerned that their use cases may subject them to having to pay for a commercial Qt license.
3. BeOS appeal.
https://www.haiku-os.org/legacy-docs/bebook/ClassesAndMethod...
Ton of projects exists, ton of cars, ton of bicycles, ton of shoes, ton of pens, ton of keyboards, mices and screens... each of them are just another one and there is no real benefit to chose one rather than another (price excepted). They exist, because someone wanted to try someting or do something. Humans do things that way.