I bet Google actually has access to its own code for Apps contacts.

Having access to the code, and having the willingness to modify it, are different things.

And yet both are different from "we don't have the source code", now aren't they?

You don't need the source! Just find where 10,000 limit is in the binary and change it to some other larger number. Assuming it's a normal 4-byte signed integer, it can go a lot higher..

Aaah, but it's in "the cloud," and the user of the software can't change even the binaries.