Sun is going to buy innotek, a low-profile PC virtualization house based in Stuttgart, and its free, open source, GPLv2-licensed VirtualBox software to extend its xVM data center virtualization platform to the desktop - particularly and especially the developer's desktop.

Sun said Tuesday that it had signed a stock purchase agreement to acquire the small, marketing-free, "internally funded" innotek. Terms were not disclosed.

Now this is not Sun's first brush up against desktop virtualization. It did of course buy the flagging Citrix-like Tarantella (which is what the old Santa Cruz Operation became after it sold Unix to SCO, née Caldera) and of course it has those Sun Ray thin clients - for which it bought Tarantella so they could run Windows. But VirtualBox is another kettle of fish.

Among other things, it's not based on Xen like Sun xVM data center-class virtualization mojo or anything else. It was built from the ground up by what Sun calls "Europe's largest and most experienced team of PC software virtualization experts."

Rather like Parallels or VMware Workstation, only more versatile, VirtualBox lets desktop or laptop PCs running the Windows, Linux, Mac or Solaris operating systems run multiple, different operating systems side-by-side, switching between them with a mouse click.

Right away you can see why Sun might find the widgetry endearing - aside from the company's model - Solaris has never been a host on a PC before.

Anyway, the software is supposed to be very friendly and performant as well as lightweight.

The download is less than 20MB and guest operating systems include all versions of Windows from 3.1 to Vista, Linux 2.2, 2.4 and 2.6 kernels, Solaris x86, OS/2, NetWare and DOS.

As part of the developer arms race, Sun figures its stock will rise if software developers can build multi-tier or cross-platform applications more easily.

It aims to give VirtualBox the support of its global development community, field resources and partners, and so drive greater adoption across a broad set of communities.

The widgetry will also give power users access to applications not available on their base operating system though Sun CTO Tim Marsland says Sun doesn't know yet how it will play the consumer card. It's also not sure whether it'll charge developers for support.

• Sun’s VirtualBox Grows Up