You really shouldn't make it open source. If your business model at all involves making money directly off these extensions, then open-sourcing it will remove any barrier whatsoever to people paying you for them. It's simply absurd.
All of my extensions are open source. I have made money off of most of them by doing support. I make money doing support even though I generally give support away for free. People are willing to pay to have faster turnaround, and to have features added that are more work than I'm willing to do in my spare time for free.
Open sourcing the extensions makes it far more likely that people will use them. It'll be more likely that they'll get improved, and maintained, and that features will be added more quickly. That is a perfect situation to offer support services. Since these extensions are for enterprise environments, it is likely that support will sell fairly well.
Respectfully,
Ryan Lane