First sorry for assuming you don't know the difference between Framework and App, but I hope the post will help someone who doesn't
vrms:
I was suggesting a topic which I find to be worth clarifying about (my guess 90% of users and 70% of developers are not 100% clear about what the licenses permit or what they restrict).
Frappe team didn't write the GPL or MIT licence they adapted them. Those licenses are public any one can read and research and even learn about their loopholes. Any good developer must have knowledge of licenses out there, so its the job of the developer and the user to educate themselves and learn requirements and obligations of each license. simple google search or youtube videos are sufficient to have understanding of different licenses.vrms:
anyone can add functionality to ERPNext using an external App.
Thats true because GPL doesn't say anything about static or dynamic linking. but any way there is just much you can do with external apps and mostly case specific modification that doesn't help generic erp.
Also, keep in mind, there is already a loophole in GPL license in which if you are not distributing your code then you don't need to release your code. For example, if you are a erpnext hosting provider and just offer a service then you don't need to release your code since you are not distributing code but service. This loophole is closed in AGPL licence but AGPL didn't prevent Odoo from going proprietary, and many companies around the world prohibit its developers from linking to AGPL code is it require open sourcing the linked programs. Whats good about ErpNext is that all developers are contributing in good faith because every one knows that popularity of ErpNext will help all.