This article at The Register was apparently what it took for me to understand why Sun's been talking about open sourcing Java so much recently.

[Competition in the cell phone OS market] has left Microsoft exposed on one flank to Java and to carrier dominated technologies such as SavaJe, and on the other to Linux. The situation becomes even graver as Sun shows increasingly strong signs that it will open source Java too, leaving Microsoft - and Symbian too - under growing pressure to adapt their models or be left behind. The clearest indication yet that the Windows giant is feeling the pressure is this week's announcement that it will introduce a measure of open source to the CE variant of its OS, which is targeted at handheld devices and the embedded market and is the basis of Windows Mobile.

Now just yesterday I found (and blogged) a good article explaining why I wouldn't open source java. But why it's even being mentioned makes a lot more sense to me after hearing it argued so succinctly.