In InDesign, you can install Hunspell dictionaries. This is software in the public domain:
Here's a blog post in InDesignSecrets.com about finding and installing Hunspell dictionaries.
I just did a Google search on "Hunspell Basque" and it appears there are Basque Hunspell dictionaries available.
Thank you John, I have submitted the requests but not heard anything. Just submitted another one.
Thank you Steve,
The dictionary is available for checking spelling but what we really need is the hyphenation facility for Basque language.
If there is a dictionary, does that mean that the hyphenation function will be there automatically?
We don't have a subscription to CC yet for this main reason (we are a Basque language publishers), so I can't check it.