 Another option is the Zero Clause BSD license, released in 2006 and aimed to software.In result, such licensed public-domain software has all four freedoms but is not hampered by the complexities of attribution (restriction of permissive licensed software) or license compatibility (issue with copyleft licensed software).See also , 

Public domain software in the early computer age was for instance shared as type-in program in computer magazines and books like "BASIC Computer Games".