What's odd is that there seem to be three different Skype apps for Android, but most people can only see one or the other available.
There's Skype available in the Market and currently at v22.214.171.1249. This lists:
Skype-to-Skype calls over 3G or WiFi
Data plan or WiFi connection required (calling in U.S - WiFi only)
Then there's Skype Mobile for Verizon, which I think is at v126.96.36.199. This one says this but doesn't mention WiFi in its description currently:
Unlimited Skype-to-Skype calls and Instant messaging without using your plan minutes
Finally the 3 network in the UK have a special version of the Skype app where you're never charged for Skype calls over their network, get that here (only works if you're on the 3 network).
It looks like the Market must be doing a check on your country (or maybe which phone network your device is locked to?) to decide which to give you, and so which restrictions to apply to you.
It looks like your device is only offering you Skype Mobile, and not Skype.
Gotta love how the phone companies are desperately trying to keep themselves relevant in the face of customers who really would rather do things another way!