For years, the license for ISX has included a built-in version of Messages+, Intelliborn's SMS app. However, if you decided you wanted to use Messages+ without using ISX, you were forced to buy a separate license for the standalone version of M+. Not any more. Earlier today, Cydia creator Saurik reached out to Intelliborn about the issue due to user complaints, and was able to get them to agree to new terms:
I have reached out to Intelliborn about this, and they agreed to allow owners of IntelliScreenX to simply be able to install Messages+ without a separate purchase. This has now been setup, and users should be able to simply install the program they want. (FWIW, this seems to just come down to confusion over what "included with" means: Messages+ was, in fact, included with IntelliScreenX... you just couldn't install Messages+ without IntelliScreenX, with which it had been included.)
Source: /r/jailbreak
I have reached out to Intelliborn about this, and they agreed to allow owners of IntelliScreenX to simply be able to install Messages+ without a separate purchase. This has now been setup, and users should be able to simply install the program they want. (FWIW, this seems to just come down to confusion over what "included with" means: Messages+ was, in fact, included with IntelliScreenX... you just couldn't install Messages+ without IntelliScreenX, with which it had been included.)
Source: /r/jailbreak