I wouldn't say that entropy coding is "separate" from dictionary / window compression. DEFLATE surely isn't the first algorithm to combine LZ77 and some form of entropy coding, and surely won't be the last.
I highly recommend that everybody go out and build an INFLATE implementation; it's a lot of fun.
I did this in javascript years ago (I had done snappy first, but wanted smaller data). It's fun and not too difficult.
The deflate side seems a little more complex. I played with it while on vacation about a month ago, but stalled after doing the LZ77 and huffman table generation, because I really just wanted to learn on the LZ77 bits worked, and I don't actually have a project that needs it.
I highly recommend that everybody go out and build an INFLATE implementation; it's a lot of fun.
Mine can be found at https://github.com/magcius/libt2/blob/master/t2_inflate.h