An example better explains my question. Force.com licenses have a Per User Limit of 10 custom objects. If there are two Force.com licenses, and you made two profiles, each with this license, would it be 10 custom objects across the whole org, or could one profile have 10 custom objects and primarily have access to those, and then the other have an additional 10 with exclusive access to those objects? Or would it be 10 total? My assumption is that if there are 2 licenses, you get 20 custom objects, but I want to be sure.
Do the limits of a Force.com license extend with purchase of additional licenses? (see description)
From the documentation it would seem that it would be possible to have 1 profile having access to 10 custom objects and another profile with access to a different 10 custom objects, but this would not grant access to all 20 custom objects to users on both profiles.
A Force.com Light App has up to 10 custom objects and 10 custom tabs, has read-only access to accounts and contacts, and supports object-level and field-level security. A Force.com Light App can’t use the Bulk API or Streaming API.
A Force.com Enterprise App has up to 10 custom objects and 10 custom tabs. In addition to the permissions of a Force.com Light App, a Force.com Enterprise App supports record-level sharing, can use the Bulk API and Streaming API, and has read/write access to accounts and contacts.
The platform licence seems to be able to access a great deal more of Salesforce and does not have an explicit limit on the number of custom objects that can be accessed specified on the documentation.
With Community licences it is possible to grant access to more custom objects than the basic 10, this is a chargeable option where access to additional custom objects can be bought in batches of 10. This may also be possible with Force.com licences but you would need to talk to your Account Executive.
Some limits are based on the number of licenses that you have. Examples of such limits are File & Storage limits and # of API calls in a 24-hour period.
These limits will usually have a minimum and maximum. Data Storage (used to store sObject records like Accounts), for example has a 1GB minimum. Each license can give you additional storage.
Say you subscribe to the Performance edition, which grants 120MB of data storage per user license. If you have 20 user licenses, you get 120MB * 20 = 2.4GB of total storage. If you only have 5 user licenses, you get 1GB instead of 600MB.
Most limits, however, are only determined by what edition of Salesforce you subscribe to (Professional, Enterprise, Unlimited). The number of custom objects seems to be locked at 50 for Professional, 200 for Enterprise, and 2000 for Performance/Unlimited.
In most cases, I don't believe there is any built-in quota system to limit the amount of platform limits on a per-user basis. In other words, if you have 2.4GB of data storage, a single (Performance) user could use all of it. If you can have a total of 20 Custom Objects, all of your users can be given permission to use all 20 of them.
The one exception I know of is for File storage (e.g. Attachments on sObject records). Each user has a quota of 2GB.
The general limits information can be found here
I believe a more extensive listing can be found here, in the developer docs