Why do some commercial apps have a section called 'also requires' and free apps don't?

Solution 1:

Furthermore where does this information actually come from?

The information is downloaded from the Ubuntu servers provided that the developers set/uploaded it when they first added the application to the Software Center catalog.

Why don't the free applications get this feature?

• As you can tell from Amnesia and other commercial apps, this "feature" lists primarily hardware requirements, not software. This is a separate Software Center catalog feature.

• Software Center lists pretty much all the "free" applications via the standard repositories, and the standard "Debian" format they use does not have such a custom field (call it hardware-depends).

• Developers of free applications can certainly choose to provide this information if they separately upload the application to Software Center instead of relying on the standard repositories. If there is a specific free application you would like to see this for, please contact the developers.

Seeing software requirements (dependencies) for free apps

If you would like to see the software a free application depends on (and will install along with it), you can try using Synaptic - an alternative but slightly more complicated package manager.

I will use the free game ExtremeTuxRacer as an example - note the second screenshot in particular:

Solution 2:

Adding to @izx's answer, the hardware requirements can be more important when paying for software ($20 in this instance). It would suck to have to find out you don't have appropriate hardware when you've already paid.