Thanks for the link. However, after reading the whole section I am left believing that using the API of an AGPL project would indeed be considered "incorporating" it.
Note how the "arms length" usage, as described, mentions completely separated software such as a shell and a notepad application.
The separation between a shell and a notepad (i.e. different applications altogether), or a kernel and a compiler (i.e. the base system and an application) seems to me clearer than the separation between an application and a library that it uses (i.e. the library is being used as part of the application in order to fulfill a feature).
here is my example that i was involved in. a proprietary software "app" wants to build a system for doing some work. They also need some accounting to be done so instead of reinventing the wheel, they were recommended to use an agpl covered accounting software as a DB. the software would send commands and the accounting package would record them and spit out reports using api.
They were told, this use case is allowed under GPL because the proprietary software was using the agpl one as a data store without any modifications. The license requirements of code share would be enough in the license file and link to the source code. Virality would not be attached in this case
Note how the "arms length" usage, as described, mentions completely separated software such as a shell and a notepad application.
The separation between a shell and a notepad (i.e. different applications altogether), or a kernel and a compiler (i.e. the base system and an application) seems to me clearer than the separation between an application and a library that it uses (i.e. the library is being used as part of the application in order to fulfill a feature).