Simplify the following text for a Grade 5 native English-speaking person.
Original: MINIX ( from `` mini-Unix '' ) was first released in 1987 , with its complete source code made available to universities for study in courses and research . It has been free and open source software since it was re-licensed under the BSD license in April 2000 .
Simplified: Released under the BSD license , MINIX is free and open source .