I've been asked quite a few times why I open-source the code. The answer is simple. Let me use an example from Joel Spolsky.
(From http://www.joelonsoftware.com/articles/fog0000000052.html)
The dominant spreadsheet, with 100% market share, is Lotus 123. You're the
product manager for Microsoft Excel. Ask yourself: what are the barriers to
switching? What keeps users from becoming Excel customers tomorrow?
... <snip: barriers to entry> ...
That's the barrier to entry. Not how hard it is to switch in: it's how hard it
might be to switch out.
And this reminded me of Excel's tipping point, which happened around the time of
Excel 4.0. And the biggest reason was that Excel 4.0 was the first version of
Excel that could write Lotus spreadsheets transparently.
Yep, you heard me. Write. Not read. It turns out that what was stopping people
from switching to Excel was that everybody else they worked with was still using
Lotus 123. They didn't want a product that would create spreadsheets that nobody
else could read: a classic Chicken and Egg problem. When you're the lone Excel
fan in a company where everyone else is using 123, even if you love Excel, you
can't switch until you can participate in the 123 ecology.
If you know that in the absolute worst case that you can still use the product even if it's shut down, then by golly, you have even less of a reason to not switch to it.