Web plugins run in the Indigo Web Server process, which currently has it's own copy of indigopy. There currently is no including across the two processes.
You should know, however, that indigoconn isn't about the SQL database - it's about the connection between python and IndigoServer. For an example of a plugin that uses the database created by the IndigoSqlClient, check out the usageReporter
in the file library.
...if an environment variable is being inherited by child processes...
If I'm understanding you, no, we aren't currently directly exposing Indigo objects to python scripts like how we expose objects in AppleScript. That may be part of the plugin API that we're developing for 5.0.