Disclaimer: Not an expert on Japanese, so if I'm incorrect anywhere, feel free to correct me. Always eager to learn more about other languages.
However, from my understanding, there really isn't many 100%, always consistent Katakana -> English translations simply because English has significantly more sounds then Japanese, which creates a lot of overlap in multiple usages of the same kana word having different translations depending on the context (i.e. ファルス, which is commonly translated as "phallus," being translated as "Falz," or シャト, which SEGA has translated as "Sato," "Shato," and "Chato," before finally settling on the French word for cat, "Chat").
So basically, without any context, kana can basically be translated to any English word that sounds similar to it, so both "Liberate" and "Rivalate" would be correct (assuming we're not automatically eliminating made-up words). While there is context in the form of the weapon's potential, written in kanji, which indicates that "Liberate" was the basis for リベレ一ト, it's always possible that SEGA always intended for リベレ一ト to be a corruption of "Liberate" instead of the word itself.
Basically, at the end of the day, both "Liberate" and "Rivalate" are accurate translations, but we don't really have any way to know what SEGA JP originally intended. The people who are most-likely to know are the localizers themselves, but considering that the game does have quite a few areas that are pretty-irrefutably inconsistently translated (such as changing the translation of "Gurhal" to "Grahl," as well as simultaneously using the "Sato" and "Chat" translation up until a recent update), I can't blame people for not wanting to give the localization team the benefit of the doubt.
EDIT: Oh right, it's also possible that "Rivalate" wasn't the original intent, but the localizers proposed it, and SEGA JP liked it and gave it the okay. Tbh, we'll probably never know since... most people probably just wouldn't be interested in a localization diary, unfortunately.