Robert Rohde wrote:
The historical position has been that absolutely nothing goes into the WMF software pool unless it is open source. As I recall, the only recognized exception was the closed source firmware running the routers at the server farm.
Also Solaris.
Lucene is free software, but was out for a while as Java wasn't free software then. I believe we used a rewritten version in C# for a while, in fact. A Java version of Lucene started being used again when Java was in the process of being freed up, I think we were using it before there was an entirely free software Java.
Well yeah, Brion took a strong stance against proprietary software and ported MediaWiki's interface to Lucene to C# to avoid having to use Java. But Lucene.NET was not very good and Robert Stojnic was keen to switch back to Java when he started working on it. Luckily by that time Sun had announced that they were making Java open source (although the source code wasn't actually published for a bit longer), so Brion could put aside his objections.
However, when we needed to scale up our file storage platform, and make backups more feasible, ZFS's snapshot feature became too attractive to resist. You can only favour idealism over pragmatism up to a point, beyond which it becomes irresponsible, and even Brion was won over. So Solaris was installed on the ms* servers.
I think the current policy is "use open source software unless you have a really good reason".
Jimmy Wales and Erik Moeller are also advocates of open source software.
-- Tim Starling