Hi Robert
That would come down to two things I think
1. If offsite it is unofficial and therefore not supported
2. If Onsite it is official and therefore would need that either
a. All snippets are tested and approved
b. A statement of "no support for custom code"
c.

Support them but charge for support given if support is requested.
It might even save them money if clients are coming up with solutions that they can later add into the core

Source code. Granted

isn't open source but this would offer a nice comparitive resource to those found on systems such as Open Commerce
Cheers
Chris