Should we have an ISV account to complete the ISV Dev Salesforce Trailhead modules?

It is actually possible to complete this module using two standard developer edition orgs.  You can create and upload the package in one org and install it (via the url) in a second org. It takes 5-10 minutes after you upload the package from the 1st org before it will be available for install but should work fine after that.  The package installs just like any other app from the App Exchange and only take a few minutes to complete. Once the package is installed, just connect to the second org from the Trailhead module and allow it to confirm that the package is present.