To be honest,
if you want any sort of exposure, it makes sense to open source any programming frameworks you produce

If you're making something important
(anything involving financial transactions, or controlling / monitoring expensive operations) you really, really want to have the source

You really don't want to be the admin of a closed system that breaks or needs maintenance

- "It's broken, fix it"
"erm, I can't"

- "We need this feature added"
"erm, I can't"

Having the source available is a prerequisite for any important, long-term project