Linus Torvalds both companies went public and Torvalds's share value temporarily shot up to roughly US$20 million. His personal mascot is a penguin nicknamed Tux, which has been widely adopted by the Linux community as the mascot of the Linux kernel. Although Torvalds believes "open source is the only right way to do software", he also has said that he uses the "best tool for the job", even if that includes proprietary software. He was criticized for his use and alleged advocacy of the proprietary BitKeeper software for version control in the Linux kernel. Torvalds subsequently wrote a free-software replacement for BitKeeper
EPOC (operating system) system to drive their next generation of devices. First, however, they needed to engineer a 16-bit single-board computer—something that was extremely difficult at the time. They codenamed the project "SIBO", for "single-board organiser" or "sixteen-bit organiser". To develop the SIBO hardware and software, they needed samples of the 16-bit microprocessors they would be programming; but it took more than a year to secure the chips, which caused a significant delay. By 1987, development of EPOC was underway: It was a single-user, preemptive multitasking operating system designed to run in read-only memory (ROM). The operating system and its programmes were written