In the old days proprietary compilers was the norm. If "blue" is of value an open source equivalent will be made eventually. But looking at the blue examples and sdesk repo I doubt it.
Going just by the examples, Blue itself seems more an incomplete templating/code generation layer for getting some syntax sugar than anything else. Like you write Blue targeting C, write super high level constructs in Blue, then include C headers and snippets of C code for all the stuff you can't write in Blue, and finally transpile Blue into C which is then compiled conventionally.