There is an N5 Starter Kit SDK which adds reference examples for the N5 series module, but for simplicity it's typically easier to point to just one source for the API as there are various different manufacturers of chipsets which support ANT.
Each manufacturer can interpret differently what each command should be named for their own platform, or could build additional features which can affect the usage of the protocol (such as variable channel count in the latest S210/S310 SoftDevice).
However, the ANT Protocol and how the functions operate do not differ between chipsets, thus there is typically a common network interface to every chip regardless of the manufacturer; Nordic Semiconductor, TI, Mobile Phone/Tablet chip manufacturers, etc. In the N5 Starter Kit SDK there is a "Network Processor" hex file which will emulate the common serial command interface seen on the TI/Nordic based C7, AT3, AP1, AP2, etc modules/chipsets. Internally that code calls different function names, but the actual behaviour of those functions remain the same.
Correct, profiles must be developed for each platform rather than a common interface, though the N5 is the first ANT SoC, and all other devices have been network processors which used the common ANT Serial Interface.