I don't know skype for asterisk from digium can be used with ip01 or those asterisk embedded IPPBX or not. I guess probably not. This is my reason to recommend siptosis for those with an linux based asterisk server.
Once you have this siptosis installed, you are in a different environment for VOIP usage.
Another site to recommend is ring2skype.com. You can get an US number for dial into skype account.