[tehprofessor]

I guess I worried licensing might be an issue with large data sets: http://neo4j.com/subscriptions/

Where using more than one instance would be desirable (I'm not trying to over optimize-- I swear! ;-_-). I suppose one server can go pretty f#€£ing far. But all the clustering requires a license (~$12k per server for start ups?) unless the code which uses it is GPL or AGPL (I think?).

Anyone who wants to explain the AGPL in layman terms would be greatly appreciated. Or specially Neo4j's application of it. To me, it seems cost prohibitive for lean startups, of one or two people.

Again, they've said contact 'em-- so it may be case by case. I could just be worrying about non-existent problems.

I tried Titan and Orient, I didn't find either as nice as Neo4j to use in my code. Though Neo4j, for me, was much more difficult to setup and use as a cluster (at the time).

... And more on topic, I'm about to install Cayley!

[JoshTriplett]

neo4j uses the GPL (specifically version 3), not the Affero GPL. You can build a service based on the community edition without sharing the source of your service; you only need to distribute source (under a GPLv3-compatible license) if you distribute your service to others.

(Summary of the Affero GPL: you must distribute the full source of your service, under an AGPL-compatible FOSS license, to the users of your service. Summary of the GPL: you must distribute the full source of your program, under a GPL-compatible license, to anyone you distribute your program to.)

It does look like the "Community" edition leaves out the clustering features, so if you need those you'd likely need a license for the proprietary version.

[kennybastani]

Neo4j is an open source graph database. The community and enterprise editions can be used in production without a license (including HA clustering). Licensing is required when you choose not to open source your code that uses Neo4j. When you have a commercial application of Neo4j, the price for the license is well justified so your customers are not impacted when an issue arises in your implementation. Most resolutions are a matter of creating an unmanaged extension that runs code embedded in the JVM.

[barakm]

If it fails in interesting ways, let me know, file a bug, etc. I'm more than happy to help.