If you distribute software that includes software that includes software that includes software who is the original licensor. Do you have to track who wrote which text and added which restrictions to track what restrictions apply to which portion of the text. When modified version of deps result in interleaved restrictions how do you decide what you can or cannot do?

The only logical thing to do is to treat such additional restrictions as poison.

> If you distribute software that includes software that includes software that includes software who is the original licensor.

In this case, the original licensor is clear: it's Neo4J, who holds the copyright on the whole thing, who have made it available under a source-available license of their choice, and who can make it available under additional license if they like — such as a proprietary license which they will sell to you.

In community open source projects which publish "software that includes software that includes software", you have to keep track of where every last line of code came from. That's called "provenance", and if you don't pay attention to it and improperly introduce code which belongs to somebody else without their permission, you're opening up both yourself and your users to legal liability.

Tracking provenance is work, but the concepts at issue are not vague.

but wasn't the point of the clause to allow licensees to remove additional clauses introduced by the original licensor?

how are licensees able to add additional clauses at all? that would violate the original license just as well.

what is the purpose of this removal clause then?

No, the point is to facilitate copyleft by ensuring that all modifications are available under the original license.

No one can add modifications which are under a new, more strict license with additional clauses. Since such clauses could be stripped away.