According to the article:
Skype’s client does not offer many of the new iOS4 features that Fring is quick to jump on, namely video calling, background operation, and even push notifications which have been around for a long time. One could argue that Fring’s client allows Skype users to use these features with Skype, which is something that users want. Skype is notoriously slow at adopting new features such as these, and is also slow at their geographical expansion. You still cannot get a Canadian Skype-In number, but there are a host of Canadian VOIP services offering phone numbers for example.
Basically, sounds like the vanilla Skype client is not ready to adopt this technology on their iPhone apps, but Fring already has, using Skype's API. This makes Skype's devs look bad, obviously, if a third party's app is surpassing their native app on their native API. Sounds like a lot of code-dick measuring as far as I'm concerned. Unfortunately, Skype still wins if Fring violated any licensing agreements (which it seems like Skype is implying)
That's an excellent point