Hi,
So sorry for the delay, I’ve missed your question somehow.
It’s not compatible with Polylang directly but back in version 1.2.8.4 we added a shortcode for handling text in different languages which should work fine with Polylang.
It allows those who run a multilanguage website to have different texts shown.
[optinforms_translate lang="en_US"]Text[/optinforms_translate]
The lang parameter accepts the language code, so if you have a website in English and Spanish you could use this as the form title
[optinforms_translate lang="en_US"]Subscribe[/optinforms_translate][optinforms_translate lang="es_ES"]Suscribir[/optinforms_translate]