I was out of town on my honeymoon (it was excellent, thank you very much) when Sun announced their choice of license for open source — or should I say free software? — Java. A few people have written to ask me my opinion on the topic, and rather more people have asked about the relevance of this change for Fedora, for gcj, and for Classpath. So, I’ve spent some time writing a post detailing my thoughts.

First Thoughts

This news is wonderful! It is the culmination of a 10 year dream to have a free software Java implementation, and not only that, it is the best possible way to to achieve the goal: having the reference implementation be the open implementation.

I’m also delighted by Sun’s choice of licenses.

Furthermore Sun is executing well on their promises. The people I’ve talked to have responded well to feedback (for instance on fixing some details in the contributor agreement) and they even were clear about the distinction between free software and open source.

I’m very optimistic that they will continue in this vein.

What about Fedora?

Naturally folks out there were eager to see OpenJDK in Fedora immediately. These initial responses are always a bit funny because the posters seem to send their messages before getting to the part of the press release explaining that not all the software is publicly available yet. Silly.

Still, the instinct is the right one. In my opinion, OpenJDK is the way to go. When we can build a complete implementation, we ought to package it and make it the default JVM on Fedora.

I think this won’t happen until at least Fedora Core 8.

Meanwhile, for Fedora Core 7 we should ship the new ecj-based gcj with support for all the new 1.5 features. This requires a bit more work, and perhaps a backport, depending on the base gcc chosen for the OS.

One issue down the road for OpenJDK adoption on Fedora is that it does not have a PPC port. Community hackers, please write this.

Oh, and when we ship OpenJDK, someone should take a good look at shipping NetBeans as well. Eclipse is wonderful and in some ways definitely better than NetBeans, but there are areas where NetBeans is superior as well.

What about Classpath?

I think our experience over the years has shown that every time we merged code bases, we gained. We gained developers, we gained quality, we gained completeness. In other words, it is better to work on a single good implementation than multiple competing implementations. (I don’t think this is a universal law, but it is true in the specific case of Java class libraries: an program where the result is relatively well-defined).

So, it is hard for me to see what role Classpath will play in the future. OpenJDK’s library will have the same license and will be the reference implementation. That argues strongly for moving Classpath development work time to OpenJDK hacking instead. (At least assuming contributor agreement stuff is cleared up … a detail.)

Classpath does have some code that the JDK does not. For instance we have some interesting AWT peers, we have a GConf back end for prefs, our HTML implementation is better, and a few other things. For the peers I think we could do separate releases (contributing these to OpenJDK is difficult or impossible — it may violate the FSF’s charter). For “pure library” bits, I’m not sure what to do 🙁

What about GCJ?

For many cases I think it will be preferable to switch entirely to OpenJDK, and not use GCJ at all.

Don’t get me wrong — GCJ is cool, and I’m proud of what we’ve done. I think we’ve solved some hard problems in creative ways. But, for many uses of Java, compatibility is the name of the game, and it is simpler to get this using the reference platform.

I think there are still areas where GCJ makes a lot of sense — embedded systems and the various platforms where there is a GCJ port but no other VM. I don’t expect it will die, but I do expect that the effort going into it will subside quite a bit. That will matter less, though, since it will be somewhat simpler for GCJ to keep pace now, since the libraries will need much less work than in the past.

Don’t Panic

Naturally this is all still contingent on things working out as they should. I’m not worried about this, and I don’t think you should worry either.

Also some patience is required. We’ll know much more in 6 months.

FOSDEM

Some folks from Sun will be at FOSDEM this year to talk about OpenJDK. And, of course, the usual Classpath and GCJ contingent will be there. I hope to see you there.