Bandwidth consumption is seen as a sign of a need being fulfilled. 5.2 Internet anonymous ftp BBS's and mailing lists. Sunsite is one machine, other sites have other machines, either broadcasting their own packages, or everybodies. The existence of such Internet-BBS's, allows others to access and broadcast material 24 hours a day, and good system administration builds up a library of relevent code packages. IE it makes Linux possible.
People contribute to public-domain, gnu and shareware for various reasons.
Projects that come out of universities get prestige for that department, and many departments hold on to valuable staff, by providing them with a work environment that makes them happy. Some commercial sites choose to purchase configuration help, installation time, and support channels from GNU suppliers. They pay for results, and like the idea that their installed code, could be supported elsewhere. The MIT university has a policy of making much of it's work available to the general public. This of course benefits other universities, who may be 'competing' with MIT, or who don't pay for the running of MIT, but MIT somehow comes to terms with that fact.