a) A SplendidCRM partner can have consultants perform the work on a work-for-hire bases. This will give the consultants access to the source code but not allow the consultants to use the source code for anything other than work for the SplendidCRM partner.
b) There is no way mix Community, Professional or Enterprise licenses within a single deployment. The Enterprise features are always used by all users. For example, the key feature of the Enterprise Edition is the workflow engine. There is no practical way to disallow the workflow engine from working for a specific set of users, nor do we believe that management would want the workflow engine to ignore events from Community users. The workflow engine is an all or nothing deal.
If the workflow engine is not important to your customer, then they should consider the Professional Edition. The key feature of the Professional Edition is the reporting engine. As before, there is no practical way to allow reporting only on records owned by Professional users and ignore records from Community users. The reporting engine is another all or nothing deal.