That would be very ugly source, as Datomic is written in Clojure and AOT compiled to Java bytecode. Due to the architecture of Clojure (especially, the use of macros) it is not exactly possible to work backwards from JVM bytecode to anything that looks like the original source code. It's not like Java where a clever decompiler can exploit output patterns generated by the Java compiler to make reasonable guesses at the structure of the source code.
But this is all besides the point; Datomic is now free (as in beer) with a great license (Apache 2.0). You can use this amazing tool for free, and you have as much need to look at the source to do so as you might need to look at PostgreSQL's source.
Some of us have been hoping for this day since Datomic was first announced, but even as an insider (I have been working at NuBank NA for less than a year) I was stunned at the speed with which this decision was made and implemented.
> Due to the architecture of Clojure (especially, the use of macros) it is not exactly possible to work backwards from JVM bytecode to anything that looks like the original source code.
I mean, presumably if you run a Java decompiler over it you'll get perfectly-legible Java source code. Just Java source code that makes a lot of calls to methods defined in the Clojure stdlib.
I'm guessing it would look a lot like what an Objective-C or Swift program looks like when you throw it into a C decompiler: a lot of boilerplate for imperatively building stack-local data structure temporaries to be passed into runtime functions, but otherwise the same code you'd expect.
> But this is all besides the point; Datomic is now free (as in beer) with a great license (Apache 2.0). You can use this amazing tool for free, and you have as much need to look at the source to do so as you might need to look at PostgreSQL's source.
Personally, I don't want to use Datomic as a tool; I want to use Datomic as a bag of parts. I want to pilfer the major components and libraries within the Datomic codebase, reusing them inside other things. (You know how CockroachDB and Clickhouse both implemented PostgreSQL-syntax-compatible binary wire protocol in part by taking the parser.y file directly from Postgres's codebase? I want to do that kind of thing, with Datomic. And probably using some pieces of Neo4j and/or Apache BEAM at the same time.) I also want to study the data structures and algorithms used to implement Datomic, to better port the concepts used in Datomic to other databases.
If Datomic was a true FOSS project, doing all of that would be simple/easy. With just a binary, though, I can't do any of that.
Some of the things that Clojure generates are valid bytecode for which there is no Java source code equivalent.
Reusing the pieces:
In general, Clojure works so well because it is all of a piece, with many decisions and subsystems working together. Datomic's source is the same way, you can't really consume just part of the elephant, even if you had the source code. Many things that Datomic does simply don't make sense at all out of context.
