Unlock w/o Front-End
Unlock is a on-chain protocol: the smart contracts are collectively governed and any application can interact with them.
There are multiple tools and applications to simplify interactions with the smart contracts, including subgraphs, a checkout UI, or the credit card gateway. However, these are completely optional, and can very well skipped entirely when building applications that integrate Unlock.
For example, this application uses the Wagmi framework to let users deploy new lock contracts, or purchase memberships from existing contracts without using any of the Unlock tools.
The Core Protocol section includes all documentation needed to build applications without using any of the example tools noted above. For example, there is a tutorial on how to use the Ethers.js library to interact with the contracts directly, and similar libraries in JavaScript or other languages can be used.