Developing accessory for iOS devices without MFi Program

Solution 1:

Yes. You'll need to obtain an MFi Program license. The cost, viability and special API access (if any) can be determined only after contacting Apple.

To get more details, and to get in touch with an Apple correspondent, check out MFi Program homepage.

Solution 2:

It appears the the resultant (software) product will be your own. It is up to you what, if any license be applied. If you choose to use source from another vendor. You need only apply their restrictions, if any. To their source (if included).

If there is no license available (listed) with their source. Its restrictions (if any) are unknown. So you should be unencumbered.