While welcoming Skype’s initiative, he described it as a "vaporware announcement" with "murky pricing details".
Writing on his blog, Robertson said he has been a vocal advocate for open standards, both in music with my company MP3.com and in VOIP with Gizmo5.
He said open standards have always give consumers more choices and ultimately better value.
"V0IP standards got a huge boost this week with two announcements," he said.
Roberston said these were Gizmo5’s launch of its SIP for Skype service called OpenSky, which lets any SIP device call Skype and receive their Skype calls, and Ebay’s announcement of Skype for SIP.
"These announcements are a huge boost for SIP as the open standard which will let calls move freely from any calling device or network," he said.
"It’s great to see Skype inching towards a more interoperable world. Even if this is a vaporware announcement at least their heart is in the right direction."
Robertson compared Skype For SIP with Skype for Asterisk, announced last year, saying that Skype’s business offering is not yet available and pricing details are murky.
In response to Robertson’s blog comments, Skype said its SIP offering is available now.
While there are other details that will undoubtedly be challenged by Skype, Robertson’s riposte will certainly give any enterprise pondering the services something to chew over.