[vidarh]

IBM has been an open source supporter for a long time. Their first Linux kernel contributions came no later than '99 (when they started upstreaming changes to support Linux on their mainframes, available since 2000).

You can see some details about their open source contributions here: http://www-03.ibm.com/linux/ossstds/oss/ossindex.html

[murukesh_s]

And Eclipse.. When it was open sourced, it was one of the largest project to be open sourced.