Computer Scrabble UI & communication protocol?
The most widely used interchange format for Scrabble games is documented at

http://poslfit.com/scrabble/gcg/

It's used for example by cross-tables.com, Quackle, (Mike Wolfberg's program) WHAT, and proprietary software for webcasts of national and world championships. 

The so-called .gcg (for "generic crossword game") format is a human-editable
text file with one line per move played so far in the game, with a list of
pragmata for identifying players, current rack if game in progress, etc.