BRL-CAD was open-sourced in 2004. MIT Scheme was released as free software in 1986 after being started somewhere near 1979 (which was about the time I started programming in Basic, using the TRS-80 and Apple II). The initial revision of the MIT git repo is dated December 1986--I think it started in RCS. The original license was some variation of the MIT one, which requested that changes be sent back to the team if at all possible, with a request to tell them what the use was. They changed to the GPL around release 7 or 8.

My first language was FORTRAN 66, learned from a book in the library, but on paper only as I had no access to a computer until a couple years later in 1979.