I know this is an old thread, but I just wanted to say I've had success making Ricotta from washed-curd whey.
I used it right after making the Gouda, and heated it to 200 F, added a little more than 1/4 C cider vinegar.
I used whey from 2 gal milk.
I ended up with 1 1/2 C Ricotta and lots of very thin whey!
Hope this helps some...