"You can't take it with you," Gill wrote in a memo sources told ZDNet News was circulated to the staff of the Denver developer. "And giving it away has been consuming more and more of my time.
"So this is to let you know that I recently sold my holdings in Quark. And over the next several years I'll be moving most of those assets to the Gill Foundation," a charitable organization he founded in 1994 to promote justice and equality "while building awareness of the contributions gay men and lesbians make to American society."
The memo did not specify who purchased Gill's share of the privately held company, ownership of which had been evenly divided between Gill and Quark CEO Fred Ebrahimi.
Quark on Wednesday confirmed Gill's departure to ZDNet News.
Gill, who the Gill Foundation Web site identifies as "one of two openly gay individuals on the 1997 Forbes 400 list," has been widely recognized as the programming genius behind QuarkXPress, Quark's flagship desktop publishing application.
"Tim founded Quark Inc. in 1981 with a $2,000 loan from his parents and has worked to build Quark into a leading developer of page-layout software for the high-end graphics market," the Gill Foundation site says.
Professionally, Gill worked for Hewlett-Packard Co. (hwp) and ALF Products, a Colorado software developer, before starting Quark.
Besides philanthropy, Gill remained vague about his future plans: "And if you want to know what I'll be doing next ... well, I promised not to add anything new to my list until after snowboarding season. After that, we'll see. Gourmet vegetarian chef, nuclear physicist, street rapper.
"The possibilities are endless."