There isn't great documentation like those projects have, but if you want to embed ChucK then you just need to include all of the C++ files in the src/core folder. To use ChucK, make a new ChucK object and then all the functions you need to call are in chuck.h:
https://github.com/ccrma/chuck/blob/master/src/core/chuck.h
A typical sequence might look something like this:
// create
the_chuck = new ChucK();
// set params (see full list at top of chuck.h)
the_chuck->setParam( CHUCK_PARAM_SAMPLE_RATE, (t_CKINT) MY_SRATE );
the_chuck->setParam( CHUCK_PARAM_INPUT_CHANNELS, (t_CKINT) MY_CHANNELS );
the_chuck->setParam( CHUCK_PARAM_OUTPUT_CHANNELS, (t_CKINT) MY_CHANNELS );
// init
the_chuck->init();
// start
the_chuck->start();
...
// add code
the_chuck->compileCode( "SinOsc foo => dac; while(true) { 2::second => now; }", "" );
// or
the_chuck->compileFile( "myChuckProgram.ck", "my:list:of:args:2:3.5" );
...
// in audio callback
the_chuck->run( inBuffer, outBuffer, numFrames );
...
// elsewhere in your application, might want to use global variables
the_chuck->setGlobalInt( "roughness", 2 );
the_chuck->broadcastGlobalEvent( "playTheSound" );