Ward publicly rejected a deal offered by the band to perform with Black Sabbath as festival headliners this year because he felt it did not recognise his long-term contribution to the band.
Negotiations continued in private until this week, when Ward published the latest details on how their talks eventually broke down.
"Throughout this process, which began over a year ago, I have had to stand up for myself time and time again," he wrote. "I have had to stand up for myself and in doing so realize my actions indirectly, although unintentionally, are upsetting and hurting a lot of you.
"I have to stand for something, and as painful as it is, I'm doing it... Nobody wins. Even the ones who thought they did."
In response, the remaining members of Black Sabbath posted the following to their official Facebook page:
"We have decided not to make any detailed comment on Bill's latest statement. There are two sides to every story. We have been working hard at rehearsals making excellent progress after Tony's treatments and we have engaged a substitute drummer for the forthcoming shows. See you at Download."
Drummer Vinny Appice is expected to replace Bill at their scheduled festival performances. Meanwhile guitarist Tony Iommi continues his battle against cancer while the band record their new album with producer Rick Rubin.