I've never heard of Hotline, even though I was heavily involved in the Apple community in the 1990s, but according to the Wikipedia page (https://en.wikipedia.org/wiki/Hotline_Communications), it looks like a good-but-shortlived product that was killed from within:

"However, a few months after Hinkley moved to Canada, he and his colleagues at Hotline Communications got into a major disagreement and Hinkley left the firm, encrypting source files for Hotline on Hotline Communication's computers, thus crippling the company."