• Identi.ca (The report refers consistently to Identica, not Laconi.ca – I know Evan’s mentioned simplifying things by renaming the Laconi.ca software to match the site name, but for now the software still lives at the Laconi.ca url)
• Jisko
• OpenMicroBlogger
• Yonkly (which doesn’t mention open source on the site, but does exist as a GPL v2 project at codeplex. Site runs ads for a SaaS version.)

As well as Prologue, which does not get grouped in with the other open source options though it is available under GPL v2. (It gets a separate group as it isn’t purely a microsharing application btu a theme for WordPress.)

It’s a good overview, though I would have liked to have seen more coverage of the difference that the OpenMicroblogging protocol (which is supported not just by OpenMicroBlogger but also by Laconi.ca) will make, in terms of real interoperability across networks. But I guess that would be less relevant to the Enterprise scenario, since the whole purpose of the enterprise scenario is to have a closed network.

(See also my post from earlier this summer listing open source microblogging options, as well as this recent post suggesting Twitter themselves could get on the open microblogging bus.)