Hi Lemustache,
Full disclaimer: I work for a small company (odatalink) that specialised in MYOB integration so i can answer a few of your questions. OdatalLink is a product we build that allows excel/powerbi/adf developers pull data directly from MYOB without the need to learn the MYOB api, config keys, etc.
1. Regarding your first question, yes, the API allows you to pull journals, accounts and jobs and none of the endpoints are currently gated behind different pricing tiers.
Caveat though: Other accounting package did recently introduce gated tiers which angered the dev community. MYOB have not made any announcements but the industry seems to follow trends so it might change.
But from my experience, MYOB is the least greedy of the big 3 and have not changed their approach to developer program/pricing/support.
2. The $110 is a recurring monthly fee as described on this page. See the table headers.
https://developer.myob.com/what-is-the-developer-program/
3. If you go down the route of rolling your own keys. No. Generally speaking, nothing further to configure other than make sure the keys exists. And the user going through the oauth flow has generally speaking high enough permissions to access the endpoint you need.
4. The oauth keys/registration is also only needed for cloud based data files. The api was available for free for those that used local/server hosting for their data file but that is disappearing with MYOB pushing everyone towards the cloud.
If you want to explore the odatalink route, you can always reach out.
Regards
Nicolas Emmerich
