Put common code in a single Script and Include it from others ...
A Workbooks Script can be very flexible and hence for security reasons Scripts are run "at arms length" in a separate environment known as a "Jail" and they access the main Workbooks service just as any other Workbooks API program does.
Do not assume your Script will always run to completion.
In addition to enforcing basic security limitations, the Jail environment allows the Workbooks Script access to a reasonable amount of memory, and processor time. The Script is killed if it exceeds the runtime you request when creating the Process or it exceeds memory and processor usage limits.
Within the Jail the Script is interpreted as PHP code and has access to a number of useful PHP libraries. These include
Web Services: xmlrpc curl
The current PHP version is 5.4; Workbooks will update this from time to time.