Java is on its way to become mostly GPL but is it too late?
Sorry to start with the spoiler, but the answer is, “No, it is not too late.” I would certainly have preferred that Sun GPL Java before Microsoft .NET was released. I think .NET would have been a total non-starter in that case. But allow me to present the evidence that Java is already kicking .NET keister on Linux.
Look at how pervasive Java has become even without the benefit of the GPL. SourceForge is one of the most if not the most popular repository of software projects for Linux (software is available for other operating systems, including Windows, but SourceForge is primarily a Linux repository). Java has enjoyed a highly prominent spot on SourceForge for a long time, well before Sun announced that it would GPL most of Java. At the time of this writing, SourceForge lists 5,421 projects written in Java. The number of Java projects outnumbers even C++ projects, at 4,582. Only 284 projects are listed for C# and only 34 projects for BASIC. I don't think it will surprise anyone that C outnumbers all others with 8,558 projects.
Here is what .NET brings to the table that Java lacks. The .NET API has richer functionality because it is not written to be a Write-Once-Run-Anywhere (WORA) platform. Java aims to be WORA, so it is missing some pretty basic features, such as good support for USB or FireWire. That's because direct support for hardware violates the WORA principle. You have to write hardware and/or platform-specific Java extension libraries that make use of the Java Native Interface to support these things.
Is that a bad thing? Must Java be faithful to WORA to be Java? In one sense, the answer is yes. The core JVM should be faithful to WORA. But that doesn't mean you can't extend Java to be platform-specific. Indeed, I hope compiled Java, in addition to the WORA JVM, gets even better as the community gets more involved in the future of Java. I am confident that only good will come of the community efforts.
I expect hardware-specific extensions to projects will flourish once Sun finishes its GPL-ization of Java. Java can remain a WORA platform for those who want to use it that way, and the community can provide the tools you need to use Java as a magnificent platform-specific language as well. So what if the add-ons violate WORA? It's a language, not a religion. In contrast, the Mono team is dead set on providing the non-WORA functions by playing catchup with the Windows API portion of .NET. All I can do is tip my hat and say, “good luck”.
The current problem with Java on Linux that is now going away is that it isn't usually a no-brainer to install Java on your favorite distribution. That's changing quickly, but it's still hit and miss. Worse, some of the best Java applications aren't available with a simple apt-get.
The apt-cache search jedit command turns up nothing, even on the future release of Ubuntu, even though jEdit is a spectacular Java-based editor. A search for the BitTorrent client Azureus brings up the GCJ-compiled version. There's nothing wrong with that, but I'd still prefer to run Azureus as a Java application. I have to download and install Azureus manually if I want the non-GCJ version. There aren't all that many professional-quality standalone client applications in Java, but the ones I love and use are rarely available from standard application repositories. I expect, or at least hope, that will change as the GPL-ization of Java progresses and a Java virtual machine is installed by default on all distributions of Linux.
But here's where Java stands to explode in usage. Currently, economy Web hosting supports MySQL and PHP by default, with perhaps Perl and maybe PostgreSQL. Java usually costs extra, most likely because it's not free, and the commercial hosts who provide these services didn't get Java installed by default. I'm betting that within one year, you'll see all those $5 or more per-month hosting services provide Java and JSP by default. I've even seen a few that already have taken this step. Could I be wrong? It's certainly possible. I was wrong once before—October 1979, I think, but I could be wrong about that. Regardless, I stand by my prediction that Java will explode on economy hosting services.
The bottom line is that if you haven't already taken the plunge, do so. Java isn't as easy to pick up as, say, PHP. But, it's enough like C/C++ that the learning curve won't be overly steep if you come from a traditional C/C++ background. I've found that the key to learning Java is to focus on how to use the error-handling features properly, which is generally where I tripped up when I first tried my hand at programming in Java.