Even in the 90s, contributions were happening as a side effect of Linux use by companies and big organizations. For example, the Ethernet drivers I used on all my servers in the late 90s were written by someone at NASA (probably as part of their work on Beowulf clusters). My company (an ISP) didn't write much code, but we gave modest $ support to open source projects, mirrored repositories, etc., because we knew OSS was crucial.