Although Tanenbaum wished for MINIX to be as easily available to students , his publisher would not allow it . Although Tanenbaum wished for MINIX to be as accessible as possible to students , his publisher was not prepared to offer material ( such as the source code ) that could be copied freely , so a restrictive license requiring a nominal fee ( included in the price of Tanenbaum 's book ) was applied as a compromise . This prevented the use of MINIX as the basis for a freely distributed software system .